Erwin Harahap

do Now or Never

6×2+7x-20=0 solve for x

Posted by Erwin on September 9, 2015

First of all, find two number p and q such that

p + q = 7
p * q = 6 * (-20) = -120

you will find out that p = 15 and q = -8
then, re-arrange the equation above as follow:

6x^2+15x-8x-20=0
(6x^2+15x)-(8x+20)=0
3x(2x+5)-4(2x+5)=0
(3x-4)(2x+5)=0

Here, we found that

3x – 4 = 0 which leads to x = 4/3
or
2x + 5 = 0 which leads to x = -5/2

so the answer for x is {-5/2, 4/3}

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