Преобразуйте в дробь выражения: а) x+2/x+3 - x-1/x б)2y- 4y²/2y-1 -1 в)5a²/5ab-b² - b/25a-5b г)x²/x³-x + 1/2-2x

а) 

x+2/x+3  -  x-1/x=

=2/x+3-1/x=

=3+1/x=(3x+1)/x

б)

2y-    4y²/2y-1   -1=

=2y-2y-2=-2

в)

5a²/5ab-b²   -   b/25a-5b=

=5a²/(b(5a-b)) - b/(5(5a-b))=

=(25a^2 -b^2)/(5b(5a-b))=

=(5a -b)(5a+b)/(5b(5a-b))=

=(5a+b)/(5b)

г)

x²/x³-x     +    1/2-2x =

=x^2/(x^3-x) + 1/(2-2x)=

=x/(x^2-1) + 1/(2*(1-x))=

=x/(x^2-1) - 1/(2*(x-1))=

=(2x-(x+1)/(2(x^2-1))=

=(x+1)/(2(x^2-1))=

=1/(2(x+1))