+128403 -2x^2 - 5x = -50 multiply through by -1
2x^2 + 5x = 50 complete the square on x
2 [x ^2 + (5/2)x ] = 50 divide both sides by 2
x^2 + (5/2)x = 25 take (1/2) of (5/2) = 5/4.....square this = 25/16, and add to both sides
x^2 + (5/2)x + 25/16 = 25 + 25/16 factor the left side and simplify the right
[ x + 5/4 ] ^2 = [ 400 + 25] / 16 take both roots
x + 5/4 = ±√ [ 425] / 4
x + 5/4 = ±5√17 / 4 subtract 5/4 from both sides
x = ±5√17 / 4 - 5/4 = [ -5 ± 5√17 ] / 4
