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# Find the value of the second derivative at a point, given the first derivative

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1. If the first derivative = 2xy, then the value of the second derivative at the point (1,2) is?
a) 6
b) 8
c) 12
d) 16

I'm stumped, i don't know how to even start a question like this. Its new to me.
Can someone help me with this question? or at least give me some steps to follow?
Thanks
2. (Original post by ksrw395)
If the first derivative = 2xy, then the value of the second derivative at the point (1,2) is?
a) 6
b) 8
c) 12
d) 16

I'm stumped, i don't know how to even start a question like this. Its new to me.
Can someone help me with this question? or at least give me some steps to follow?
Thanks
You have f ' (x) = 2xy

Differentiate both sides with respect to x to get
f '' (x) = 2x(dy/dx) + 2y

Using the product rule. Now plug in the co-ords to get the gradient.
3. (Original post by Zacken)
You have f ' (x) = 2xy

Differentiate both sides with respect to x to get
f '' (x) = 2x(dy/dx) + 2y

Using the product rule. Now plug in the co-ords to get the gradient.
I did that and i got 12.
Thanks
4. (Original post by ksrw395)
I did that and i got 12.
Thanks
No problem.

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