1) 2x^ + 3x -5 = 0 a=2 b=3 c=-5 D=9 + 40 = 49 = 7^ x1 = -3 + 7/ 4 = 1 x2 = -3 - 7/ 4 = -2,5 2) 5x^ - 7x + 5 = 0 a=5 b=-7 c=5 D=49 - 100 = -51 Корней нет. 3) -x^ + 7x + 8 = 0 a=-1 b=7 c=8 D=49 + 32 = 81 = 9^ x1= -7 + 9/ -2 = -1 x2 = -7 - 9/ -2 = 8