瑞安市中医院网上预约:题目^^^^^^急~~~~~~~~~~

来源:百度文库 编辑:查人人中国名人网 时间:2024/05/03 10:46:21
(x+1)(x+3)(x+5)(x+7)+15
分解因式
把式子列出来

(x+1)(x+3)(x+5)(x+7)+15
=[(x+1)(x+7)][(x+3)(x+5)]+15
=(x^2+8x+7)(x^2+8x+15)+15
=(x^2+8x+11)^2-1
=(x^2+8x+12)(x^2+8x+10)
=(x+2)(x+6)(x^2+8x+10)

设x+4=y
有(y-3)(y-1)(y+1)(y+3)+15=(y2-9)(y2-1)+15=y4-10y2+24=(y2-4)(y2-6)=((x+4)2-4)((x+4)2-6)

=(x^2+8x+7)(x^2+8x+15)+15
=(x^2+8x)^2+22(x^2+8x)+120
=X^4+16x^3+86x^2+88x+120