Need help taking the derivative

Question

thatonegirl_ · Answer

$$f(x)=(x-1)^2(x+3)$$

jackthegreatest · Answer

hmm looks like chain rule to me

thatonegirl_ · Answer

but wouldn't it just be multiplied by 1

thatonegirl_ · Answer

so you don't really have to use it. But it is product rule right?

jackthegreatest · Answer

correct product rule for sure

thatonegirl_ · Answer

ight so what i'm getting is
2(x-1)(x+3)+(x-1)^2

thatonegirl_ · Answer

but the answer says it's (x-1)(3x+5)

thatonegirl_ · Answer

after they simplified it from something else..

jackthegreatest · Answer

im pretty sure it is this:
2(x-1)(x-1)(x+3)+(1)(x-1)^2

thatonegirl_ · Answer

Why did you get 2 (x-1)s in the beginning?

jackthegreatest · Answer

shoot haha it should be the deriv of that whoops, which is 1

jackthegreatest · Answer

yeah so you were right

jackthegreatest · Answer

2(x-1)(x+3)+(x-1)^2
did you try simplifying?

thatonegirl_ · Answer

Lol okay xD And yeah i got it to 2x^2-4x-6+(x-1)^2 but then i left it bc i'm pretty sure that's not what the answer is

thatonegirl_ · Answer

ooh what they did was they solved it then just used the power rule

thatonegirl_ · Answer

so i mean it should still give me the same answer.. i'll see lol

jackthegreatest · Answer

you should get 3x^2 +2x - 5

thatonegirl_ · Answer

so i got x^3-x^2-5x+3

thatonegirl_ · Answer

oh oops forgot to take the derivative

thatonegirl_ · Answer

lol

jackthegreatest · Answer

$$2x^2+4x−6+x^2−2x+1$$

jackthegreatest · Answer

there that gets you
3x^2 +2x-5

jackthegreatest · Answer

we basically had the same thing, except (x+3)(x-1) does not make -4x

thatonegirl_ · Answer

so how come the product rule didn't work for this one?

jackthegreatest · Answer

if you factor
3x^2+2x-5
you get
(3x+5)(x-1)

jackthegreatest · Answer

it does, just that you didnt multiply correct haha, you had the write idea

thatonegirl_ · Answer

ohh okay lol thanks so much! :)

jackthegreatest · Answer

np