Whats the number?
2007-09-09 16:49:51 · 6 answers · asked by erin j 2 in Science & Mathematics ➔ Mathematics
5x^2 + 12x = 32
x < 0 (since they tell you the number is negative)
5x^2 + 12x = 32
Subtract 32 from both sides:
5x^2 + 12x - 32 = 0
Factor:
(5x - 8)(x + 4) = 0
5x - 8 = 0
x = 8/5
x + 4 = 0
x = -4
Since x<0, x = -4
Check answer:
5(-4)^2 + 12(-4)
= 5*16 - 48
= 80 - 48
= 32
The answer checks.
2007-09-09 16:59:01 · answer #1 · answered by whitesox09 7 · 0⤊ 0⤋
We need to solve 5x^2 + 12x -32 = 0, and the quadratic formula can be used. But this can be factored into (5x-8)(x+4), so the roots are 5/8 and -4. Since a negative number was requested, it is -4.
2007-09-09 17:01:09 · answer #2 · answered by Anonymous · 0⤊ 0⤋
Say the negative number is N.
5*N^2 + 12N = 32, N<0 (since negative)
5N^2 + 12N -32 = 0, see if you can factor.
(5N -8)(N +4) = 0, so
5N-8 = 0 | N+4 = 0
N = 8/5 | N = -4.
Check if N = -4 really works.
2007-09-09 16:58:01 · answer #3 · answered by pbb1001 5 · 0⤊ 0⤋
5(-x)^2 +(12)(-x) =32
5x^2 -12x -32 = 0
(5x+8)(x-4)=0
x = 4 or x = -8/5
X= -4 is the answer.
2007-09-09 17:05:20 · answer #4 · answered by ironduke8159 7 · 0⤊ 0⤋
5x^2 + 12x = 32
5x^2 + 12x - 32 = 0
(5x - 8) (x + 4) = 0
x = 8/5, -4
You want the negative answer, which is -4.
2007-09-09 16:58:00 · answer #5 · answered by Shiny Moogle 1 · 0⤊ 1⤋
5x^2+12x=32
5x^2+12x-32=0
x=(-6+sqrt(36+160))/5
x=(-6+16)/5
x=2 is not negative
ANSWER:
x=-22/5
2007-09-09 16:57:42 · answer #6 · answered by iyiogrenci 6 · 0⤊ 2⤋