(1/x^2+3x+2)+(1/x^2+5x+6)+(1/x^2+7x+12)
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写错了吧，估计应该是1/(x^2+3x+2)+1/(x^2+5x+6)+1/(x^2+7x+12)
1/(x^2+3x+2)+1/(x^2+5x+6)+1/(x^2+7x+12)
=1/((x+1)(x+2))+1/((x+2)(x+3))+1/((x+3)(x+4))
=((x+3)(x+4)+(x+1)(x+4)+(x+1)(x+2))/((x+1)(x+2)(x+3)(x+4))
=(3x^2+15x+18)/((x+1)(x+2)(x+3)(x+4))
=(3(x+2)(x+3))/((x+1)(x+2)(x+3)(x+4))
=3/((x+1)(x+4))
=3/(x^2+5x+4)
1/(x^2+3x+2)+1/(x^2+5x+6)+1/(x^2+7x+12)
=1/((x+1)(x+2))+1/((x+2)(x+3))+1/((x+3)(x+4))
=((x+3)(x+4)+(x+1)(x+4)+(x+1)(x+2))/((x+1)(x+2)(x+3)(x+4))
=(3x^2+15x+18)/((x+1)(x+2)(x+3)(x+4))
=(3(x+2)(x+3))/((x+1)(x+2)(x+3)(x+4))
=3/((x+1)(x+4))
=3/(x^2+5x+4)
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原式=1/（x+1)(x+2)+1/(x+2)(x+3)+1/(x+3)(x+4)
=1/(x+1)-1/(x+2)+1/(x+2)-1/（x+3)+1/(x+3)-1/(x+4)
=1/(x+1)-1/(x+4)
=(x+4-x-1)/(x²+5x+4)
=3/(x²+5x+4)
祝你开心
=1/(x+1)-1/(x+2)+1/(x+2)-1/（x+3)+1/(x+3)-1/(x+4)
=1/(x+1)-1/(x+4)
=(x+4-x-1)/(x²+5x+4)
=3/(x²+5x+4)
祝你开心
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(1/x^2+3x+2)+(1/x^2+5x+6)+(1/x^2+7x+12)
=1/[(x+1)(x+2)]+1/[(x+2)(x+3)]+1/[(x+3)(x+4)]
=1/(x+1)-1/(x+2)+1/(x+2)-1/(x+3)+1/(x+3)-1/(x+4)
=1/(x+1)-1/(x+4)
=3/[(x+1)(x+4)]
=1/[(x+1)(x+2)]+1/[(x+2)(x+3)]+1/[(x+3)(x+4)]
=1/(x+1)-1/(x+2)+1/(x+2)-1/(x+3)+1/(x+3)-1/(x+4)
=1/(x+1)-1/(x+4)
=3/[(x+1)(x+4)]
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