Question

Which represents all the values of x that make the rational expression 2x-4 over x-5 undefined?

x = 2
x = 5
x = –5 or x = –2
x = 2 or x = 5

Answer 1

For this case we have the following expression:

`\frac {2x-4} {x-5}`

By definition, we have the expression undefined when the denominator is 0.

So:

`x-5 = 0`

Adding 5 to both sides of the equation:

`x-5 + 5 = 5\\x = 5`

Thus, the expression is undefined when
`x = 5.`

Answer:

Option B