6n^2+7n-20=0
a=6, b = 7, c = - 20
-b+/- sqrt(b^2 - 4ac) - 7 +/- sqrt( 7^2 -4*6(- 20))
x = ----------------------------- = ---------------------------------------
2a 2*6
- 7 +/- sqrt 529 - 7 +/- 23
x = ----------------------------- = ------------------
12 12
x = ( -7 - 23)/12 = - 30/12 = - 5/2 and
x = ( - 7 + 23)/12 = 16/12 = 4/3