(10/(25-b²)-1/(5+b)+1/(5-b))*(25-10b+b²)=
=((10-5+b+5+b)/(5-b)(5+b))*(5-b)²=
=((10+2b)(5-b))/(5+b)=
=(50-2b²)/(5+b)=
=2(25-b²)/(5+b)=
=2(5-b)(5+b)/(5+b)=
=10-2b.
(10/(25-b²)-1/(5+b)+1/(5-b))*(25-10b+b²)=
=((10-5+b+5+b)/(5-b)(5+b))*(5-b)²=
=((10+2b)(5-b))/(5+b)=
=(50-2b²)/(5+b)=
=2(25-b²)/(5+b)=
=2(5-b)(5+b)/(5+b)=
=10-2b.