What is the sum of all values of y for which the expression (y + 1)/(y^2 - 5y + 4 + y^2 - 6y) is undefined?
When the denominator is 0, the fraction is undefined. the denominator in this problem is y^2 -5y +4 +y^2 -6y.
We want this to be 0, so I add that at the end.
y^2 -5y +4 +y^2 -6y=0
We can simplify this.
2y^2 -11y +4=0
Bring that into the quadratic equation, and then you should have the answer.
Hope this helps.