2x^2-5x-12=0
solve by completing the square.
please explain how it's sovled.
A perfect square is,
(a+b)^2=a^2+b^2+2ab
So you have to adapt the equation given to this expression.
The term with x should be of the form 2ab, but a=sqrt(2)x, so b=5/(2*sqrt(2)), then
2x^2-5x-12=(sqrt(2)*x)^2+sqrt(2)*x*5/(2*sqrt(2))+25/8-25/8-12=0
(sqrt(2)x+5/(2sqrt(2)))^2=121/8
x=4; x=-3/2