Question

Find the zeros of the function.

f(x) = 4x^3 - 12x^2 - 40x

Answer 1

f(x) = 4x^3 - 12x^2 - 40x

0 = 4x^3 - 12x^2 - 40x

4x^3 - 12x^2 - 40x = 0

4x(x^2 - 3x - 10) = 0

what's the next step?

Answer 2

Distribute?

Answer 3

distributing will only get you back to 4x^3 - 12x^2 - 40x = 0

so you'll be going backwards

Answer 4

Well I'm not sure then.

Answer 5

you need to factor x^2 - 3x - 10

Answer 6

now factor the quadratic part

Answer 7

(x-5)(x+3)

Answer 8

close but no

Answer 9

-5 times 3 = -15 and not -10

Answer 10

No, sorry I ment to put 2 it was a typo

Answer 11

good, x^2 - 3x - 10 factors to (x-5)(x+2)

Answer 12

The keys are next to each other lol

Answer 13

lol that's ok, happens to me all the time too

Answer 14

Thanks for the help:)

Answer 15

f(x) = 4x^3 - 12x^2 - 40x

0 = 4x^3 - 12x^2 - 40x

4x^3 - 12x^2 - 40x = 0

4x(x^2 - 3x - 10) = 0

4x(x-5)(x+2) = 0

4x = 0 or x-5 = 0 or x+2 = 0

x = ?? or x = ?? or x = ??

Answer 16

yw

Answer 17

@jim_thompson5910 , I have another queston, do you need a 0 in that too?

Answer 18

what do you mean

Answer 19

x=5 x=-2 do you need x=0?

Answer 20

yes x = 0 is a solution

there should be 3 solutions total

Answer 21

Oh, okay. Thanks:)

Answer 22

if you were to start with f(x) = 4x^3 - 12x^2 - 40x and plug in x = 0, you would get f(x) = 0 as a result

Answer 23

so that proves x = 0 is a solution

yw