已知x(x+1)(x+2)(x+3)+1=25,求x²+3x的值.
问题描述:
已知x(x+1)(x+2)(x+3)+1=25,求x²+3x的值.
答
x (x+1) (x+2) (x+3) + 1 = 25交换次序x (x+3) (x+1) (x+2) + 1 = 25(x²+3x) (x²+3x+2) = 24(x²+3x)² + 2(x²+3x) = 24设 A = (x²+3x)则 A² + 2A - 24 = 0(A+6)(A-4) = 0A = (x...