(x+1)(x+2)(x+3)-6*7*8 设A=x+2 (A-1)A(A+1)-6*7*8 =(A^3-A)-(7^3-7) =(A^3-7^3)-(A-7) =(A-7)(A^2+7A+49-1) =(x-5)[(x+2)^2+7(x+2)+48] =(x-5)(x^2+11x+66)