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Math Help - Evaluating

  1. #1
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    Evaluating

    4x^2 + 3 when x = 5
    103

    Evaluate 2a - 3 when a = -5
    -13

    Evaluate -2a + 6b when a = 6 and b = -3
    -30
    Not sure if it should be -12a + -18b tho

    Evaluate (x + 1) 2 - 5 when x = -3
    -9

    Evaluate c - 3d when c = 1 and d = 1/3


    0.1

    Or should it be c - 0.9d?



    x + x^3 - 4 x^4 when x = 2
    -54
    Not sure if this should be -54x


    5a + 3a^2 when a = -3
    12 or 12a?

    Find F when c = 15 in the formula F = 9C/5 + 32


    F = 59

    *mistook it for an almost-identical question in which all that was different was that c = 30



    I'm not sure if I should leave the variables in or not.


    Last edited by gfy010; May 18th 2010 at 12:18 PM.
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  2. #2
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    Quote Originally Posted by gfy010 View Post
    Evaluate 4x^2 + 3 when x = 5
    103 Correct

    Evaluate 2a - 3 when a = -5
    -13 Correct

    Evaluate -2a + 6b when a = 6 and b = -3
    -30 Correct

    Not sure if it should be -12a + -18b tho No, you're right the first time.

    Evaluate (x + 1)^2 - 5 when x = -3
    -9 Incorrect. Should be -1

    Evaluate c - 3d when c - 1 and d = 1/3 Don't understand this one. What does c equal?


    0.1

    Or should it be c - 0.9d?



    x + x^3 - 4 x^4 when x = 2
    -54 Correct
    Not sure if this should be -54x No


    5a + 3a^2 when a = -3
    12 or 12a?Answer is 12

    Find F when c = 15 in the formula F = 9C/5 + 32


    F = 86 Incorrect. Should be 59



    I'm not sure if I should leave the variables in or not.

    Hi gfy010,

    See my results in red.
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  3. #3
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    ah, thanks*

    I messed up some of the questions, edited the first post now.

    Tho I'm not sure about ( x + 1 ) 2 - 5 when x = -3

    Are you sure it's not -3 + 1, then 2 * -2, then -4 - 5?

    It's not the parenthesis to the second power (which would be positive 4), it's the parenthesis * positive 2.
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  4. #4
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    Quote Originally Posted by gfy010 View Post
    ah, thanks*

    I messed up some of the questions, edited the first post now.

    Tho I'm not sure about ( x + 1 ) 2 - 5 when x = -3

    Are you sure it's not -3 + 1, then 2 * -2, then -4 - 5?

    It's not the parenthesis to the second power (which would be positive 4), it's the parenthesis * positive 2.
    I misinterpreted your writings. I assumed since the 2 was on the right side of the parenthesis, you wanted to square the contents.

    If you're just multiplying by 2, then your answer is correct. It is -9.
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  5. #5
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    Ah, good to know, thanks again.
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