make bottom number same
ok, so remember
(a-b)(a+b)=a²+b²
so
to get from (y-x) to (y²-x²), multiply 2nd fraction by (y+x)
so multiply 2nd fraction by (y+x)/(y+x)
[tex] \frac{2x}{y^2-x^2}- \frac{(y+x)(x)}{y^2-x^2} [/tex]=
[tex]\frac{2x-x(x+y)}{y^2-x^2}[/tex]=
[tex]\frac{2x-x^2-xy}{y^2-x^2}[/tex]
