七年级下数学问题
1/（x-1）+1/x（x+1）+1/（x+1)(x+2)+1/(x+2)(x+3),计算。（一定是要用简便方法的）、题目很长，我前面的没打，帮忙了。...
1/（x-1）+1/x（x+1）+1/（x+1)(x+2)+1/(x+2)(x+3),计算。（一定是要用简便方法的）、题目很长，我前面的没打，帮忙了。
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恩
1/(x-1)x+1/x(x+1)+1/(x+1)(x+2)+1/(x+2)(x+3)
=[1/(x-1) - 1/x]+[1/x - 1/(x+1)]+[1/(x+1) -1/(x+2)]+[1/(x+2) - 1/(x+3)]
=1/(x-1)-1/(x+3)=4/[(x-1)(x+3)]
.
1/(x-1)x+1/x(x+1)+1/(x+1)(x+2)+1/(x+2)(x+3)
=[1/(x-1) - 1/x]+[1/x - 1/(x+1)]+[1/(x+1) -1/(x+2)]+[1/(x+2) - 1/(x+3)]
=1/(x-1)-1/(x+3)=4/[(x-1)(x+3)]
.
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1/(x-1)x+1/x(x+1)+1/(x+1)(x+2)+1/(x+2)(x+3)
=[1/(x-1) - 1/x]+[1/x - 1/(x+1)]+[1/(x+1) -1/(x+2)]+[1/(x+2) - 1/(x+3)]
=1/(x-1)-1/(x+3)=4/[(x-1)(x+3)]
=[1/(x-1) - 1/x]+[1/x - 1/(x+1)]+[1/(x+1) -1/(x+2)]+[1/(x+2) - 1/(x+3)]
=1/(x-1)-1/(x+3)=4/[(x-1)(x+3)]
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=[1/(x-1) - 1/x]+[1/x - 1/(x+1)]+[1/(x+1) -1/(x+2)]+[1/(x+2) - 1/(x+3)]
=1/(x-1)-1/(x+3)=4/[(x-1)(x+3)]
=1/(x-1)-1/(x+3)=4/[(x-1)(x+3)]
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1/x（x+1）=1/x-1/(1+x)
1/（x+1)(x+2)=1/(1+x)-1/(x+2)
1/(x+2)(x+3)=1/(x+2)-1/(x+3)
1/（x-1）+1/x（x+1）+1/（x+1)(x+2)+1/(x+2)(x+3)=
1/（x-1）+1/x-1/(1+x)+1/(1+x)-1/(x+2)+1/(x+2)-1/(x+3)=
1/（x-1）+1/x-1/(x+3)
1/（x+1)(x+2)=1/(1+x)-1/(x+2)
1/(x+2)(x+3)=1/(x+2)-1/(x+3)
1/（x-1）+1/x（x+1）+1/（x+1)(x+2)+1/(x+2)(x+3)=
1/（x-1）+1/x-1/(1+x)+1/(1+x)-1/(x+2)+1/(x+2)-1/(x+3)=
1/（x-1）+1/x-1/(x+3)
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