计算：(1)"1/6x-4y"+"1/6x+4y"-"3x/4y^2-9x^2" (2)1-(a- "1/1-a")^2除以"a^2-a+1/a^2-2a+1"
问题描述：
计算：(1)"1/6x-4y"+"1/6x+4y"-"3x/4y^2-9x^2" (2)1-(a- "1/1-a")^2除以"a^2-a+1/a^2-2a+1"
答
1)"1/6x-4y"+"1/6x+4y"-"3x/4y^2-9x^2"
=1/(2(3x-2y))+1/(2(3x+2y))-3x/((2y-3x)(2y+3x))
=((3x+2y)+(3x-2y)+2*3x))/(2(3x-2y)(2y+3x))
=6x/((3x-2y)(2y+3x))
=6x/(9x^2-4y^2)
(2)1-(a- "1/1-a")^2除以"a^2-a+1/a^2-2a+1"
=[(1-a)^2+(1-a)]/(1-a)^2 除以"a^2-a+1/(a-1)^2"
=(2-3a+a^2)/(a^2-a+1)