what value of x is the fraction undefined

1). 1 / x^2 -3x + 2
2). X^2 + 3^2 + 36/ x2 - 3x- 10
3). 18/x + X^2 +1/X^2 -9
4). X^2+10/x^2+4x-5 -
2-X1/x^2+8+15
( pls show workings)?

The fraction undefined when the denominator = 0:

1. x^2-3x+2 = 0.
(x-1)(x-2) = 0
x-1 = 0, X = 1.
x-2 = 0, X = 2.
The fraction is undefined when X = 1. and 2.