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Question 1121043: If f(7)=-5, g(7)=2, f'(7)=3, and g'(7)=-1, find (2f.3g)'(7). Show your calculation.
Found 2 solutions by greenestamps, ikleyn:
Answer by greenestamps(13203)   (Show Source):
You can put this solution on YOUR website!
Unless you are using some nonstandard notation, the value of (2f.3g)'(7) is just
(2*f'(7))*(3*g'(7)) = (2(3))*(3(-1)) = 6(-3) = -18
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Yes; thanks, tutor ikleyn. I did not recognize the notation as the derivative of a product.
Answer by ikleyn(52818)  (Show Source):
You can put this solution on YOUR website! .
If f(7) = -5, g(7) = 2, f'(7) = 3, and g'(7) = -1, find (2f.3g)'(7). Show your calculation.
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The correct solution is THIS:
(2f.3g)'(7) = 2f'(7)*3g(7) + 2f(7)*3g'(7) = (2*3)*(3*2) + (2*(-5))*(3*(-1)) = 66.
It uses standard formula for derivative of a product
(u*v)' = u'*v + u*v'.
The tutor @greenestamps misread the problem and inadvertently gave incorrect solution.
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