help on factoring`

[Guest]

i got this problem wrong and i did not know what i did wrong....

i was asked to factor 18+7x^2-x^4 and i factored it to (x^2+2)(x^2-9)


what did i do wrong????

 

[Guest]

Hello!

do what you can......ummmm........keep trying factor it out and ummmm...whatever

 

[JOSE JAIME-RODRIGUEZ]

You need one more step which is to simplify the factors:
(x^2-9) (x^2+2)....now you can finish it.

 

[Chief343]

18+7x^2-x^4

Multiply by -1

x^4-7x^2-18

=(x^2-9)(x^2+2)


Factor, Difference of two squares x^2+-9

(x-3)(x+3)

Answer


(x^2+2)(x-3)(x+3)

 

[soroban]

Hello, brendaursula!

I was asked to factor $\displaystyle 18\,+\,7x^2\,-\,x^4$ and I factored it to $\displaystyle (x^2\,+\,2)(x^2\,-\,9)$

What did i do wrong?

Two things . . .

(1) If you multiply out your answer, you get: $\displaystyle \,x^4\,-\,7x^2\,-\,18$
$\displaystyle \;\;\;$which is not what they gave you.

(2) $\displaystyle x^2\,-\,9$ can be factored, so you aren't finished yet.


I suspect you factored by taking out a -1 first: $\displaystyle \;-1(x^4\,-\,7x^2\,-\,18)$

Then we get: $\displaystyle \:-1(x^2\,+\,2)(x^2\,-\,9)$

Replace the$\displaystyle \,-1:\;\;(x^2\,+\,2)(\underbrace{9\,-\,x^2})$
. . . . . . . . . . . . . . . . . . . . diff. of squares
. . . . . Answer: \(\displaystyle \x^2\,+\,2)\overbrace{(3\,-\,x)(3\,+\,x)}\)

 

[ERIK VARGAS]

ok, you have(x^2+2) (X^2-9).
in your first set of parqantheses it is a differrnce of two squares and you cannot further find the square of 2.
( x^2-9) is a difference of two squares .
since 2 does not have a square find the square of negative nine which does have a square
(x^2+2) (x-3) (x+3) you will end up with this outcome