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

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 ${y}^{2} - 3 y + 2 = 0$
Solve for $y$ the denominator using the quadratic formula:
${y}_{1 , 2} = \frac{3 \pm \sqrt{9 - 8}}{2}$
${y}_{1} = 2$
${y}_{2} = 1$