a平方-9分之2a-a-3分之1=2a/[(a+3)(a-3]-(a+3)/[(a+3)(a-3)]=(a-3)/[(a+3)(a-3)]=1/(a+3)x^2=2x平方-1分之(x-1)平方+x+1分之x平方=[(x-1)^2+x^2(x-1)/(x^2-1)=[(x-1)^2+2(x-1)/(x^2-1)=(x^2-1)/(x^2-1)=1...