Question 767787
ax^2+bx+c
4x^2+8x-5=0

since a*c=-20

we use 10 and -2 as follows


4x^2+10x-2x-5=0

2x(2x+5)-1(2x+5)=0

(2x-1)(2x+5)=0

so x=1/2 or x=-5/2

and so 

(x-1)(x+5)=0

x^2-6x-5=0


:)