Question

How do you find all the values that make the expression undefined: `(y^2 + 2y - 3)/(y^2 - 3y + 2)`?

Answer 1

Your expression turns undefined if you choose `y` such that you get a division by ZERO (it cannot be done!).
You need to find the value(s) of `y` that can make your denominator equal to zero, or `y^2-3y+2=0`
Solve for `y` the denominator using the quadratic formula:
`y_(1,2)=(3+-sqrt(9-8))/2`
`y_1=2`
`y_2=1`
Which are the two values you need.