
Berlin V.
asked 12/22/23Basic partial derivative verification question
I have F=y'(1+x2y'), and I need to find ∂F/∂y and ∂F/∂y'
The answer I get for ∂F/∂y is 0, which is the correct one. However for ∂F/∂y' I should get 1+2x2y', but for some reason I get 1+2x2y'+y'x2. Could someone please tell me where I went wrong?
My try: Using the product rule we get ∂F/∂y'=∂/∂y'(y')(1+2x2y')+y'∂F/∂y'(1+x2y')=1*(1+2x2y')+y'x2.
2 Answers By Expert Tutors
Ariel O. answered 12/26/23
Highly Skilled Tutor for Math, Computer Science and Physics
F = y'(1+x2y')
= y' + x2y'2
∂F/∂y' -> treat x2 as constant
= 1 + 2x2y'
∂F/∂y -> treat y' and x2 as constant
= 0 + 0
= 0
Ben W. answered 12/23/23
Experienced High School & College Level Tutor with a PhD in Math
It might help to rewrite your steps because it seems like you just miscopied one number. Since the pieces for your product rule are y' and 1+x^2y', the product rule says ∂F/∂y'=∂/∂y'(y')(1+x2y')+y'∂F/∂y'(1+x2y')=1*(1+x2y')+y'x^2, which simplifies to the answer you want.
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Daniel B.
12/22/23