x^2+x -56=0D = 225x1=-8x2 =7x^2 -x - 2 =0D = 9x1= -1x2 =2x^2 -4x - 5 =0D= 36x1=-1x2 =5x^2 + 8x + 12 = 0D=16x1=-6x2 =-2x^2 +4x + 7 = 0D= -12 (корней нет)