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(a+1)(a+2)(a+3)-6x7x8

题目详情
(a+1)(a+2)(a+3)-6x7x8
▼优质解答
答案和解析
(a+1)(a+2)(a+3)-6*7*8
令x=a+2
原式=(x-1)x(x+1)-(7-1)*7*(7+1)
=x^3-x-7^3+7
=(x^3-7^3)-(x-7)
=(x-7)(x^2+7x+49)-(x-7)
=(x-7)(x^2+7x+49-1)
=(x-7)(x^2+7x+48)
=(a+2-7)(a^2+4a+4+7a+14+48)
=(a-5)(a^2+11a+66)