Question

given the function f(x)+x^3+5x^2-x-4, find
a) f'(-2)
b) the values of 'a' such that f'(a)=56

Answer 1

My eyes are bad, are you looking for the derivative ?

Answer 2

For A, plug -2 in x, for B, find the a such that 56 = d/da (a³+5a²-a-4)

Answer 3

*f=(x)

Answer 4

ok thanks

Answer 5

*f = (x) ?

Answer 6

56 = a³+5a²-a-4*

Answer 7

you mean f(a) or f'(a) with ' ?

Answer 8

sorry *f(x)=, i accidently put "f(x)+" in my question

Answer 9

f'(a)

Answer 10

what about b and c? do you put ' on purpose or what? YOu need derivative?

Answer 11

Well, in this case, derivative the function. Do you know how to?

Answer 12

is the derivative of the function 2x^2+10x-1-0?

Answer 13

and then you plug in f(-2)?

Answer 14

No. That is not the derivative. Try again.

Answer 15

Close, it's 3x² + 10x - 1

Answer 16

Now plug in -2.

Answer 17

sorry thats what i was meant to put

Answer 18

plug in -2 for b.

for c, find x such that 56 = 3x² + 10x - 1

Answer 19

ok thank you

Answer 20

Welcome. Do you know what to do?

Answer 21

is it 12-20-1
which gives me -9?

Answer 22

For A, yes.

Do you know how to deal with b?

Answer 23

just about to do it

Answer 24

do you solve it to get two answers?

Answer 25

?

Answer 26

answers x=3, x=-19/3 ?