How does 12x^5 + 5x^6 +1 equal -63 when x= -2? Please explain

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    Watching an exam solutions video on stationary points, and he substitutes x= -2 into y=12x^5 + 5x^6 + 1, which gives him -63 as the value for y.

    When I do this is situation though, I get an answer nothing like -63.

    I was doing 12(-2^5) + 5(-2^6) + 1, which didn't give me -63. I also tried (12*-2)^5 + (5*2)^6 + 1, which again, didn't give me -63.

    Can someone please walk me through how you get y=-63 for the answer of that equation when you substitute x=-2?

    Would be a real relief it's been stressing me out all day.

    Thanks
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    Well you have 12*(-2)^5 + 5(-2)^6 +1
    = 12*-32 +5*64 +1
    = -384 + 320 + 1
    = -63


    (Make sure when you do -2 to a power the -2 is in brackets like (-2)^5 not -2^5
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    (Original post by blobbybill)
    Watching an exam solutions video on stationary points, and he substitutes x= -2 into y=12x^5 + 5x^6 + 1, which gives him -63 as the value for y.

    When I do this is situation though, I get an answer nothing like -63.

    I was doing 12(-2^5) + 5(-2^6) + 1, which didn't give me -63. I also tried (12*-2)^5 + (5*2)^6 + 1, which again, didn't give me -63.

    Can someone please walk me through how you get y=-63 for the answer of that equation when you substitute x=-2?

    Would be a real relief it's been stressing me out all day.

    Thanks
    To correctly evaluate it you should be following bidmas rules

    So

    12(-2)^5+ 5(-2)^6 + 1

    -2 to the power of 6 should be a positive result as would any even power (minus x minus = plus) but entering it as you are doing your calculator will work out 2^6 and then make it negative.


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    If the first '+' was a '-' it works. Typo?

    Edit: Whoops. Ignore that!
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    (Original post by Bruhh)
    Well you have 12*(-2)^5 + 5(-2)^6 +1
    = 12*-32 +5*64 +1
    = -384 + 320 + 1
    = -63


    (Make sure when you do -2 to a power the -2 is in brackets like (-2)^5 not -2^5
    If you were doing a positive number, ie 2^5, would the 2 need to be in brackets so it would be (2)^5, or does it only need to be in brackets if its a negative number?
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    (Original post by blobbybill)
    If you were doing a positive number, ie 2^5, would the 2 need to be in brackets so it would be (2)^5, or does it only need to be in brackets if its a negative number?
    it doesnt need to be but imo its a good idea to put anything you substitute in into brackets
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    (Original post by blobbybill)
    If you were doing a positive number, ie 2^5, would the 2 need to be in brackets so it would be (2)^5, or does it only need to be in brackets if its a negative number?
    It doesn't need to be, but as mentioned above it's good practice to so you know that the whole part is being raised to the power.
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    Equation
    When X = -2
    Put take the value of x as - 2 in the given equation


    Note:
    Even powers of negative numbers = a positive number:
    Odd powers of negative numbers = a negative number

    12(XX.X.X.X) + 5(X.X.X.X.X.X) = (12 X -32) + (5 X64) + 1= -384 + 320 + 1= -384 + 321= - 6 YAY!!:party::party:
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    The answer: -63 is correct.
    Follow the rules of bidmas. -2^5 is -32. And 2^6 is 64.
    -32*12 is -384 + (64*12) +1= 63. Sorry if I'm not being clear i'm typing on my phone.
 
 
 
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