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Single-Variable Expressions Practice Questions (page 3)

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Updated on Oct 3, 2011

Practice 3

  1. Add y and 11y by adding the coefficients and keeping the base and exponent: 1 + 11 = 12, so y + 11y = 12y.   Replace y with 6 and multiply:  

    12(6) = 72

  2. Subtract 8n from 12n. Remember, subtract the coefficient of 8n from the coefficient of 12n and keep the base and exponent:  

    12n – 8n = 4n  

    The expression is now 4n + 7.  

    Replace n with 9:  

    4(9) + 7  

    Multiplication comes before addition in the order of operations:  

    4(9) = 36  

    The expression is now 36 + 7.  

    Add: 36 + 7 = 43.

  3. Add 2r2 and 3r2 by adding the coefficients and keeping the base and exponent:   2r2 + 3r2 = 5r2  

    Replace r with –3:   5(–3)2  

    Exponents come before multiplication in the order of operations:   (–3)2 = 9   The expression is now 5(9).  

    Multiply: 5(9) = 45.

  4. Replace every h with 4:  

    4(4) – 8(4) + 6((4) + 2)  

    Begin with addition inside the parentheses:  

    4 + 2 = 6  

    The expression is now:  

    4(4) – 8(4) + 6(6)  

    Multiplication comes before subtraction or addition, so multiply next:  

    4(4) = 16  

    8(4) = 32  

    6(6) = 36  

    The expression is now:  

    16 – 32 + 36  

    Add –32 and 36:  

    –32 + 36 = 4  

    The expression is now:  

    16 + 4  

    Add: 16 + 4 = 20.

  5. None of the terms in the expression 5s + s2 – 9 can be combined because they are unlike terms. Replace every s with –2:   5(–2) + (–2)2 – 9  

    Work with the exponent first:  

    (–2)2 = 4  

    The expression is now:  

    5(–2) + 4 – 9  

    Multiplication comes before addition or subtraction, so multiply next:  

    5(–2) = –10  

    The expression is now:  

    –10 + 4 – 9  

    You can add before subtracting (or you can subtract before adding):  

    –10 + 4 = –6  

    The expression is now:  

    –6 – 9  

    Finally, subtract: –6 – 9 = –15.

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