Question

x+y分之y - y^2-x^2分之xy

Answer 1

1

x+y分之y-y^2-x^2分之xy

=y/(x+y)-xy/(x+y)(y-x)

=[y(y-x)-xy]/(x+y)(y-x)

=y^2-2xy/(y+x)(y-x)

2.

1 - [a-（1/1-a)]/（a^2-a+1）/(a^2-2a+1）

=1-[（a-a^2+1）/(1-a)] / [（a^2-2a+1）/(a^2-a+1）]

=1-[(a^2-a+1)/(a-1)] x[(a-1)^2/(a^2-a+1)]

=2-a

=2+1/4 =9/4