x2+3x-4 = 0
D = 32-4*1*(-4)
D = 9+16
D = 25
x1 = -3+√25/2*1
x1 = -3+5/2*1
x1 = 2/2
x1 = 1
x2 = -3-√25/2*1
x2 = -3-5/2*1
x2 = -8/2
x2 = -4