^ - знак степени
1)a^2/(ax-x^2) + x/(x-a)= a^2/[x(a-x)] - x/(a-x)= (a^2-x^2)/[x(a-x)]=
=[(a-x)(a+x)] / [x(a-x)] = (a+x)/x
2)(b^2-4by)/(2y^2-by) - 4y(b-2y)= (b^2-4by)/[y(2y-b)] +4y/(2y-b)=
=(b^2-4by+4y^2)/[y(2y-b)]= (b-2y)^2 / [-y(b-2y)]=(2y-b)/y
3)(x-25)/(5x-25) + (3x+5)/(x^2-5x)=(x-25)/[5(x-5)]+(3x+5)/[x(x-5)]=
=[x(x-25)+5(3x+5)]/[5x(x-5)]= (x^2-25x+15x+25)/[5x(x-5)]=
=(x^2-10x+25)/[5x(x-5)]=(x-5)^2/[5x(x-5)]=(x-5)/5x