1-y^2

__________
y^2-4y-5

there is no equal sign.so to what is that equated to

factor it ...

= (1-y)(1+y) / ( (y-5)(y+1) )
= (1 - y)/(y-5) , y ≠ -1

To simplify the expression (1 - y^2) / (y^2 - 4y - 5), we can start by factoring the numerator and the denominator if possible.

Let's factor the numerator first:
1 - y^2 = (1 - y)(1 + y)

Now let's factor the denominator:
y^2 - 4y - 5 = (y - 5)(y + 1)

Now we can rewrite the expression as:
(1 - y)(1 + y) / (y - 5)(y + 1)

Next, we can check if there are any common factors in the numerator and denominator that can be canceled out. In this case, there are no common factors to cancel.

So, the simplified expression is:
(1 - y)(1 + y) / (y - 5)(y + 1)