Question

If g(x) = x^2 f(x), f(4) = 3 and f'(4) = -5, then g'(4) =?

Answer 1

differentaite both sides you g'(x)=2xf(x)+x^2f'(x) (by product rule)
g'(4)=8f(x)+16f'(x)=24-80=-56

Answer 2

You know product rule right?

Answer 3

f'g + fg'

Answer 4

yeah so just apply it here g=x^2 and f is f only

Answer 5

wait y do u have to use g=x^2 and f =f ...didnt u answer te hquestion already and get -56

Answer 6

err yeah i was just explaining how i got the answer \m/

Answer 7

im still kinda confused

Answer 8

after u differentiated

Answer 9

If you want to get the answer just use product rule differentiate and get substitue the given values where exactly are u confused?

Answer 10

oh ok nvr mind....i was confused with how u got thsoe numbers, i forgot to substite

Answer 11

after i differentaited i put x=4 as you want g'(4) you know 2x=8,f(4)=3 and f'(4)=-5 i just substitued those in the equation i got to get the answer.

Answer 12

awesome...thanks! =) i get the problems after i see how to approach it

Answer 13

if i post anotehr problem on teh side can u help me

Answer 14

Yeah sure....