八年级分式2道计算题!(1)1/6x-4y - 1/6x+4y +3x/4y^2-9x^2(2)1/1-x +1/1+x +2/1+x^2 +4/1+x^4

问题描述:

八年级分式2道计算题!
(1)1/6x-4y - 1/6x+4y +3x/4y^2-9x^2
(2)1/1-x +1/1+x +2/1+x^2 +4/1+x^4

(1)1/6x-4y - 1/6x+4y +3x/4y^2-9x^2
=[6x+4y-(6x-4y)-12x]/(36x^2-16y^2)
=(8y-12x)/(36x^2-16y^2)
=4(2y-3x)/[4(3x+2y)(3x-2y)]
=-1/(3x+2y)
(2)1/1-x +1/1+x +2/1+x^2 +4/1+x^4
=2/(1-x^2)+2/(1+x^2)+4/(1+x^4)
=4/(1-x^4)+4/(1+x^4)
=8/(1-x^8)
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