Question

已知x方-5x=14,求（x-1）（2x-1）-（x+1）方+1的值

Answer 1

x方-5x=14

x方-5x-14 = 0

(x+2)(x-7) = 0

x = -2,或x = 7

x = -2时：

（x-1）（2x-1）-（x+1）方+1 = -3*（-5）-（-1）方+1 = 15-1+1 = 15

x = 7时：

（x-1）（2x-1）-（x+1）方+1 = 6*13-（-7）方+1 = 78-49+1 = 30