Question

HELP PLEA

Answer 1

@jim_thompson5910

Answer 2

The first thing I would do is factor out x


f(x) = 9x^3 + 18 x^2 - 135x
f(x) = x(9x^2 + 18x - 135)

Answer 3

now use the quadratic formula to solve 9x^2 + 18x - 135 = 0

Answer 4

after dividing all by 9 to make your life easier

Answer 5

true, I didn't realize that 9 was also part of the GCF

Answer 6

f(x) = 9x^3 + 18 x^2 - 135x
f(x) = 9x(x^2 + 2x - 15)

now solve x^2 + 2x - 15 = 0

Answer 7

can you write out the general steps for me in how to solve these kinds of problems; not necessarily with this one but for any of these problems just so i can have a general reference?

Answer 8

is it just :

1.) factor out x
2.) use quadratic formula?

Answer 9

in this case, you can factor out 9x

Answer 10

inmost cases can i do that?

Answer 11

f(x) = 9x^3 + 18 x^2 - 135x
f(x) = 9x(x^2 + 2x - 15) ... factor out the GCF 9x

set each factor equal to 0 and solve

9x = 0 leads to x = ???

x^2 + 2x - 15 = 0 leads to x = ??? or x = ???

use the quadratic formula to solve the equation x^2 + 2x - 15 = 0

Answer 12

There are several different approaches to solving quadratic equations. You'd benefit by making a list and learning how to apply each one:

quadratic formula
factoring
factoring by grouping
completing the square
graphing

and so on ... there are others.

In this case, regard yourself lucky that 9x can be factored out; no, in general, you will not be that fortunate.

Answer 13

its -b + or - squarroot b^2-4ac/2a

Answer 14

but i don't have a calculator with me currently.

Answer 15

yes
\[\Large x = \frac{-b\pm\sqrt{b^2-4ac}}{2a}\]
is the quadratic formula


use this as a calculator if you don't have one
http://web2.0calc.com/

Answer 16

ok thanks ill calculate it real quick

Answer 17

I got 3.8 and -7.8

Answer 18

@jim_thompson5910

Answer 19

or 3 and -5

Answer 20

you should get two whole numbers

Answer 21

solving x^2 + 2x - 15 = 0 for x gives

x = 3 or x = -5