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

1. 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, I have a test on differentiation and coordinate geometry tomorrow and this was on an exam solutions video on finding stationary points and the nature of them

Thanks
2. (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, I have a test on differentiation and coordinate geometry tomorrow and this was on an exam solutions video on finding stationary points and the nature of them

Thanks
Have you remembered that an odd power of -2 will give you a minus but an even power will give you a plus? your first version is the correct one, i.e. 12 ( -32) + 5( +64)+1

Updated: October 13, 2016
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