Evaluating expressions with one variable (article) | Khan Academy (2024)

A mixture of explanations, examples, and practice problems to have you evaluating expressions with one variable in no time!

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  • Joy

    4 years agoPosted 4 years ago. Direct link to Joy's post “I still don't understand ...”

    Evaluating expressions with one variable (article) | Khan Academy (2)

    I still don't understand the challenge problems e⋅e−5ee, dot, e, minus, 5, e when e=5e=5e, equals, 5.What does this mean?

    (76 votes)

    • Littleman0562

      4 years agoPosted 4 years ago. Direct link to Littleman0562's post “so, e(dot)e - 5e, the dot...”

      Evaluating expressions with one variable (article) | Khan Academy (5)

      Evaluating expressions with one variable (article) | Khan Academy (6)

      Evaluating expressions with one variable (article) | Khan Academy (7)

      so, e(dot)e - 5e, the dot symbol represents multiplication. And 5e is another way to represent multiplication so, the expression actually looks like this: 5x5 - 5x5 which equals to 0 because 5x5 = 25, and 5x5 = 25, and subtracting 25 with 25 = 0.

      e(dot)e - 5e
      5x5 - 5x5 = 25 - 25
      25 - 25 = 0

      (181 votes)

  • Morgan, Aaron

    5 years agoPosted 5 years ago. Direct link to Morgan, Aaron's post “If 9-8/x = ? and x=4 what...”

    Evaluating expressions with one variable (article) | Khan Academy (9)

    If 9-8/x = ? and x=4 what do I do with the 8/x? Do I multiply add divide or subtract?

    (38 votes)

    • David Severin

      5 years agoPosted 5 years ago. Direct link to David Severin's post “you substitute for x, so ...”

      Evaluating expressions with one variable (article) | Khan Academy (12)

      Evaluating expressions with one variable (article) | Khan Academy (13)

      Evaluating expressions with one variable (article) | Khan Academy (14)

      you substitute for x, so 9 - 8/4, do divide (8/4) first then subtract from 9.

      (61 votes)

  • Smith Dalton

    6 years agoPosted 6 years ago. Direct link to Smith Dalton's post “Why do we have to do mult...”

    Evaluating expressions with one variable (article) | Khan Academy (16)

    Why do we have to do multiplication and division first? Why to use these "order of operation"?

    (15 votes)

    • moralisaiah

      6 years agoPosted 6 years ago. Direct link to moralisaiah's post “Here is why; "Because exp...”

      Evaluating expressions with one variable (article) | Khan Academy (19)

      Evaluating expressions with one variable (article) | Khan Academy (20)

      Here is why; "Because exponents are simply repeated multiplication, they are performed before multiplication. ... Thus the order: parentheses first, exponents second, mutiplication and division third, and save the lowest level operations of addition and subtraction for last." Personally I believe order of operation is way to balance the equation as well. :)

      (47 votes)

  • kme

    5 years agoPosted 5 years ago. Direct link to kme's post “If you don't know what y ...”

    If you don't know what y is, then you won't get an exact answer

    (18 votes)

    • Intellectual Genius

      5 years agoPosted 5 years ago. Direct link to Intellectual Genius's post “Well you don't need to kn...”

      Evaluating expressions with one variable (article) | Khan Academy (24)

      Evaluating expressions with one variable (article) | Khan Academy (25)

      Well you don't need to know what y is to solve the question. For example you have:6t=48. (if something is written like 6t, that always means you have to multiply, or any variable). So we have: 6t=48, we can divide both sides by 6 (we are dividing because you always do the inverse of what you are trying to solve, the opposite of multiplication is division)

      we have to divide both sides by 6

      6t=48, 6/6 cancels out, 48/6=8. So now the equation would look like this: t=8, and now we know what t is we can verify it. 6t=48 or 6x8=48.

      And that's the beauty of Algebra!

      If you need more help just tell me.
      -Intellectual Genius

      (33 votes)

  • jonathan.christen

    6 years agoPosted 6 years ago. Direct link to jonathan.christen's post “what is it asking me when...”

    what is it asking me when it says Evaluate 2y2y when y = 6y=6

    (16 votes)

    • Kim Seidel

      6 years agoPosted 6 years ago. Direct link to Kim Seidel's post “It means you use substitu...”

      Evaluating expressions with one variable (article) | Khan Academy (29)

      Evaluating expressions with one variable (article) | Khan Academy (30)

      It means you use substitution... You replace the "y" in "2y" with the value you are given. Since you were told to use "y=6", you take out "y" and replace it with 6. Remember, "2y" means "2 times y", so you need a multiplication symbol. Thus, "2y" becomes "2(6)".
      Then, you simplify the expression by doing the multiplication. Your final answer would be 12.

      Hope this helps.

      (27 votes)

  • Mateo Gonzalez

    10 months agoPosted 10 months ago. Direct link to Mateo Gonzalez's post “is it just me or is it wa...”

    is it just me or is it way easier here than in class?

    (23 votes)

    • stargirl9th

      9 months agoPosted 9 months ago. Direct link to stargirl9th's post “way easier”

      way easier

      (3 votes)

  • IHateStudying

    3 years agoPosted 3 years ago. Direct link to IHateStudying's post “i can't understand the qu...”

    i can't understand the question nine please help me understand

    (18 votes)

    • pompano [hurt lol]

      3 years agoPosted 3 years ago. Direct link to pompano [hurt lol]'s post “Start out with the variab...”

      Evaluating expressions with one variable (article) | Khan Academy (37)

      Start out with the variable. What is d worth? What do you need to do with that variable in the sentence? You should see that d is worth 4, and we need to now add that in the sentence.

      The sentence should now look like this -
      8/4 + 3

      Now, solve it like you would usually do it. 8/4 is equal to 2 (We need to do it first since it is the second in the Order of Operations), and then add 3 to that 2. You should get an answer of 5 if you did all that calculation correctly.

      Hope this helped!

      (15 votes)

  • Rclxqvs_

    a year agoPosted a year ago. Direct link to Rclxqvs_'s post “How do you do this with f...”

    How do you do this with fractions? (I'm really bad with fractions and math)

    (11 votes)

    • Kim Seidel

      a year agoPosted a year ago. Direct link to Kim Seidel's post “The process is no differe...”

      Evaluating expressions with one variable (article) | Khan Academy (41)

      The process is no different. You replace each variable with its given value. Then you simplify the expression following order of operations rules and the rules for working with fractions. If you aren't great at working with fractions, then do yourself a favor and get more practice on that topic.

      (15 votes)

  • Drunkenstein

    5 years agoPosted 5 years ago. Direct link to Drunkenstein's post “Does this topic have viab...”

    Does this topic have viable application to non-Algebra subjects, if any? Thanx.

    (11 votes)

    • Kim Seidel

      5 years agoPosted 5 years ago. Direct link to Kim Seidel's post “Absolutely! There are ma...”

      Evaluating expressions with one variable (article) | Khan Academy (45)

      Absolutely! There are many formulas that get used in real life situations. This teaches you how to use a formula and calculate a result based upon replacing values into the formula.

      (20 votes)

  • jayden farrow

    4 years agoPosted 4 years ago. Direct link to jayden farrow's post “so u saying if i put 5 + ...”

    so u saying if i put 5 + 2b and be equal to 5 the answer would be 15

    (14 votes)

    • Gibson Jameson Harvey

      a year agoPosted a year ago. Direct link to Gibson Jameson Harvey's post “If b=5 then yes it does. ...”

      If b=5 then yes it does. it means this 5+2x5

      (6 votes)

Evaluating expressions with one variable (article) | Khan Academy (2024)

FAQs

How to evaluate expressions with one variable? ›

To evaluate, substitute the given value for the variable in the expression and simplify using the order of operations. To follow the order of operations, you always need to do any multiplication/division first before any addition/subtraction.

How do you evaluate the expression for the given values of the variable? ›

To evaluate an algebraic expression, you have to substitute a number for each variable and perform the arithmetic operations. In the example above, the variable x is equal to 6 since 6 + 6 = 12. If we know the value of our variables, we can replace the variables with their values and then evaluate the expression.

Can a single variable be an expression? ›

Also, is a single variable like x or k consider as a mathematical expression? Example (1) 5yx^2 (2) 6K (3) a^3(xyz) (4) x (5) 8 (6) A ( note that all these are a single term of a polynomials in one or more variables of any degree.) Yes, “7”, “x”, and “k” are mathematical expressions.

Can an expression have more than one variable? ›

The basics of algebra taught us how to express an unknown value using letters such as x, y, z, etc. These letters are called here as variables. An algebraic expression can be a combination of both variables and constants. Any value that is placed before and multiplied by a variable is a coefficient.

How to evaluate expressions in 7th grade? ›

An expression can combine arithmetic operations with numbers, letters, or both. Letters are used to represent variables. To evaluate an expression, find the value of the expression by replacing each variable in the expression with a given number. Two expressions are equivalent if they represent the same amount.

How do you evaluate an expression step by step? ›

The order of operations should always be used to evaluate the expression. For any given expression, this means solving within the parentheses, then the exponents, then multiplying or dividing from left to right, and finally adding or subtracting left to right. Not following this order will give the incorrect answer.

What are the steps to solving equations involving one variable? ›

Step 1: Using LCM, clear the fractions if any. Step 2: Simplify both sides of the equation. Step 3: Isolate the variable. Step 4: Verify your answer.

What is an example of a single variable equation? ›

The quantity on one side of the equals sign must have the same value as the quantity on the other side of the equals sign. For example, 11 − 6 = 5 , x + 4 = 12 , 3 x − 6 = 9 , and x 2 − 5 = 4 are all equations with a single variable.

What is an example of a variable expression? ›

A variable is a letter that represents an unknown quantity. In an expression, the variable represents that part of the expression that is unknown or that could change. For example, 10 + x means "10 plus something." The "something" is unknown, which is why it is represented with a variable instead of a specific number.

What is the difference between an expression and an equation? ›

The difference is that expressions do not include an equal sign and are basically mathematical “phrases.” Equations include an equal sign, and show equivalency between two mathematical expressions. For example, 2x + b is an algebraic expression, but 2x + b = 14 is an algebraic equation.

What are the four types of algebraic expressions? ›

Types of Algebraic Expressions
  • Monomial.
  • Binomial.
  • Trinomial.
  • Polynomial.
  • Multinomial.

Does an expression always have a variable? ›

No, an expression doesn't necessarily need to have a variable.

How do you evaluate a function with a variable? ›

Evaluating a function means to substitute a variable with its given number or expression. Given f(x) = 2x + 4, evaluate f(5). This question asks you to substitute 5 for x and simplify. To add functions, add their outputs; to subtract functions, subtract their outputs.

How do you find the value of one variable? ›

Step 1: Simplify both sides of the equation. Step 2: Move all of the parts containing the variable you are solving for to the same side of the equation. Step 3: Isolate the variable using inverse operations.

How do you find the equation of one variable? ›

The linear equations in one variable is an equation which is expressed in the form of ax+b = 0, where a and b are two integers, and x is a variable and has only one solution. For example, 2x+3=8 is a linear equation having a single variable in it. Therefore, this equation has only one solution, which is x = 5/2.

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