分解因式(x+1)(x+3)(x+5)(x+7)+15

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分解因式(x+1)(x+3)(x+5)(x+7)+15
分解因式(x+1)(x+3)(x+5)(x+7)+15

分解因式(x+1)(x+3)(x+5)(x+7)+15
原式=(x+1)(x+7)(x+3)(x+5)+15
=(x^2+8x+7)(x^2+8x+15)+15
令x^2+8x=y
原式=(y+7)(y+15)+15
=y^2+22y+120
=(y+10)(y+12)
=(x^2+8x+10)(x^2+8x+12)

原式=
[(x+3)(x+5)][(x+7)(x+1)]+15
=(x^2+8x+15)(x^2+8x+7)+15
=(x^2+8x)^2+22(x^2+8x)+105+15
=(x^2+8x)^2+22(x^2+8x)+120
=(x^2+8x+10)(x^2+8x+12)
=(x^2+8x+10)(x+6)(x+2)