Question 98461
Assuming that the problem is
{{{(y^2+y-20)/(y^2-2y-8)}}}
Factorise the top and bottom expressions.
{{{((y+5)(y-4))/((y+2)(y-4))}}}
The denominator could not be zero so y can't be 4 or -2.
Cancel out the common factor.
{{{((y+5)cross(y-4))/((y+2)cross(y-4))}}}
{{{(y+5)/(y+2)}}}