Question

2y^2-5y-12=0 how would you solve by completing the square?

Answer 1

Move the "non X" term to the right:
2y² -5y = 12

Divide the equation by the coefficient of X² which in this case is 2
y² -2.5y = 6

(There's more)

Answer 2

take the coefficient of y which is -2.5

divide it by 2
-1.25

square that number
-1.25² = 1.5625

then add it to both sides of the equation.
y² -2.5y + 1.5625= 7.5625

Take the square root of both sides of the equation:
y -1.25 = sqrt(7.5625)
y = 1.25 + 2.75
y = 4

sqrt(7.5625) also equals -2.75
y -1.25 = -2.75
y = -1.5
Source for completing the square:
http://1728.org/quadr2.htm