For how many values of x is the function

Please help!!!!!!!!!!!!!!

I am assuming that you mean 

For how many values of x is the function $y=\dfrac{x-2}{x^2-7x+10}$ undefined?

As the denominator is a quadratic function, there are 2 values of x which makes the function $y=\dfrac{x-2}{x^2-7x+10}$ undefined.

For how many values of  x is the function     

$y=\frac{x-2}{x^2-7x+10}\;\;\text{undefined}$

$y=\frac{x-2}{(x-2)(x-5)}$

you cannot divide by zero so x cannot be 2 or 5.   this graph will have holes or asyptotes.

So this is fucntion for all real values of x except for x=2 and x=5

It will be a function in the following domain.

(-infiny,2), (2,5), (5,infity)

cancel down and you get

$y=\frac{1}{x-5}\\ $

This is a hyperbola.  The asyptotes are x=5 and y=0 but there will be a hole at (2,-1/3)

here is the graph: