巧笑倩兮
春芽
共回答了12个问题采纳率:83.3% 举报
1/(1-x)+1/(1+x)+2/(1+x^2)+4/(1+x^4)
=(1+x+1-x)/(1+x)(1-x)+2/(1+x^2)+4/(1+x^4)
=2/(1-x^2)+2/(1+x^2)+4/(1+x^4)
=2(1+x^2+1-x^2)/(1-x^2)(1+x^2)+4/(1+x^4)
=4/(1-x^4)+4/(1+x^4)
=4(1+x^4+1-x^4)/(1-x^4)(1+x^4)
=8/(1-x^8)
x/(1+x)-1/(1-x)-(x^3-2x+1)/(x^2-1)
=x/(1+x)+1/(x-1)-(x^3-2x+1)/(x^2-1)
=(x^2-x+1-x^3+2x-1)/(x^2-1)
=(-x^3+x^2+x-1)/(x^2-1)
=[-x^2(x-1)+(x-1)]/(x^2-1)
=(x-1)(1-x^2)/(x^2-1)
=-(x-1)
=1-x
=1-(-2)
=3
1年前
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