Question 916854
y^2 -25/y^2 -3y-10 

factor both the numerator and the denominator

the numerator is a difference of two squares of the form x^2 - y^2 = (x-y)(x+y)

(y-5)(y+5)/(y-5)(y+2) = 

What's in common?  y-5

Divide out y-5

= (y+5)/(y+2)