2c/bd与3ac/4b^2通分2c/bd=2c*4b/(4b^2*d)=8bc/(4b^2*d)3ac/4b^2=3ac/(4b^2*d)2xy/(x+y)^2与x/x^2-y^2 求过程和最简公分母2xy/(x+y)^2=2xy*(x-y)/[(x+y)^2*(x-y)]x/x^2-y^2=x/[(x+y)*(x-y)]=x*(x+y)/[(x+y)^2*(x-y)]...