# Math Help - using the quadratic formula

1. ## using the quadratic formula

I need help factoring this trinomial:

12x^2 -88x+112 =0

I tried using the quadratic formula and getting:
x=90.02758... or 85.9724.... which both don't make any sense whatsoever. I think I am making mistakes simplifying the quadratic formula. I get to [88 +/- sqrt(2368)]/24

What next?

my course is saying the factors are:

x=5.694 or 1.639

2. ## Re: using the quadratic formula

Originally Posted by jmanna98
I need help factoring this trinomial:
12x^2 -88x+112 =0
First simply the question: $3x^2-22x+28=0$.

3. ## Re: using the quadratic formula

hi jmanna98

you can first divide the first equation by 4,getting:
3x^2-22x+28=0

$x_{1/2}=\frac{-(-22)\pm \sqrt{22^2-4\cdot 3\cdot 28}}{2\cdot 3}$

can you simplify this now?

4. ## Re: using the quadratic formula

where does the $-88$ come from thot $b=(-22)$

$x=\frac{-b\mp\sqrt{b^2-4ac}}{2a}$

5. ## Re: using the quadratic formula

oh yes you are right.i will correct that now.thanks!

6. ## Re: using the quadratic formula

Yes that made things easier. Thanks for that

7. ## Re: using the quadratic formula

Originally Posted by jmanna98
OK: 3000x^2 -3000x - 6000 = 0 ; x = ?

8. ## Re: using the quadratic formula

Originally Posted by jmanna98
I need help factoring this trinomial:

12x^2 -88x+112 =0

I tried using the quadratic formula and getting:
x=90.02758... or 85.9724.... which both don't make any sense whatsoever. I think I am making mistakes simplifying the quadratic formula. I get to [88 +/- sqrt(2368)]/24
According to my calculator, $\sqrt{2368}= 48.66$, to two decimal places. Adding 88 gives 136.66 and dividing that by 24, 5.69 as your course gives.

Oh, I see what your error is. You have [88+/- sqrt(2369)]/24, which is correct, but you did 88+/- sqrt(2368)/24! Do you see the difference? The [ ] means you do the sum and difference before dividing by 24. If you entered, on your calculator, "88+ sqrt(2368)/24" you will be dividing only the square root by 24, not the sum. Either use parenthesis keys or, simpler, press the "=" key before the square root.

What next?

my course is saying the factors are:

x=5.694 or 1.639
I hope it didn't! The roots of the equation are 5.694 and 1.639 (to three decimal places) but the factors of the trinomial are 12(x- 5.694)(x- 1.639).

9. ## Re: using the quadratic formula

Originally Posted by Wilmer
OK: 3000x^2 -3000x - 6000 = 0 ; x = ?
first you should divide everything by 3000 to get:
Spoiler:
x^2-x-2=0

10. ## Re: using the quadratic formula

Hmmm...I was asking jmanna98, the original poster...to see if he could now handle these...