Question 258986
I suspect you are missing some parentheses.
(y^2-25)/(y^2-16)*(y^2-4y/2y+10)
should be 
(y^2-25)/(y^2-16)*(y^2-4y)/(2y+10)

{{{(y^2-25)/(y^2-16)*(y^2-4y)/(2y+10)}}}
begs to be

(y^2-25)/(y^2-16)*y(y-4)/2(y+5)

{{{(y^2-25)/(y^2-16)*y(y-4)/2(y+5)}}}


((y-5)*(y+5))/((y-4)*(y+4))*(y(y-4))/(2(y+5))

{{{((y-5)*(y+5))/((y-4)*(y+4))*(y(y-4))/(2(y+5))}}}



(y-5)/(y+4)*(y)/(2)

{{{(y-5)/(y+4)*(y)/(2)}}}