Question

For what value of x will (x-1)(x+2)/x+2 be undefined

Answer 1

When setting the factored denominator to 0, you get that x+2=0, x=-2. So, x cannot be -2.

Answer 2

Using the property that anything over 0 is undefined, we can set x+2 to 0 and solve it to find the undefined points.
$x+2 = 0$
$x = -2$
So when x is -2, the equation will be undefined because of the rules about division by zero.