For what values of the variable is the rational expression undefined?

Question

I have 2 problems and no Idea how to work them:

3/(x-5) I guessed 5 and 8/(x+2) and guessed 4 I reduced the 8 and 2

Answer 1

The only time a rational expression is undefined is when the denominator is equal to zero.
So, set the denominators equal to zero and solve for x.
x-5 = 0 and x+2 = 0

You have to ignore the numerators when you are looking to make the expression undefined.

Hope this helps. Good Luck.

Answer 2

In the second example, you cannot reduce the 8 and the 2. Put a 6 in for the x. You would have 8/8 or 1 if you do not reduce. Now try it with your reduced answer. You would have 4/6, or 2/3.

You cannot cancel any thing within the parentheses. You can only cancel factors of both the numerator and denominator.

Now to answer the original question, in order to find all values of the variable for which the the expression is undefined, set the denominator equal to zero (you know that you cannot divide by zero) and solve the resulting equation.

x-5=0, x=5

x+2=0, x=-2

Hope I've helped

Answer 3

both expressions are undefined when the "bottom line" = 0
ie x-5 = 0 hence x = 5
and x + 2 = 0 hence x = -2

Answer 4

division by zero is undefined

therefore

the first expression is undefined when x = 5
the second expression is undefined when x = -2

Answer 5

for the first expression, it is undefined when x=5

the 2nd expression: undefined when x=-2

Answer 6

3/(x-5)...
this expression is undefined for x=5
8/(x+2)....
do..............x=-2