2x^2+x-28=0

Solve by completing the square

1 answer

2x^2+x = 28
divide by 2
x^2 + x/2 = 14
add 1/16 to both sides
x^2 + x/2 + 1/16 = 14 + 1/16
x+1/4)^2 = 225/16
x + 1/4 = ± 15/4
x = -1/4 ± 15/4 = 7/2 or -4