Determine when the rational expression below is undefined:
(x + 1)(x-2)
(2x-8)

When x = 4

Step-by-step explanation:

Division by zero is undefined. With real numbers, you are not allowed to divide by zero. Any value of x that causes the denominator to have a value of zero is not allowed. We need to find out which values of x cause the denominator to equal zero.

To do that, we set the denominator equal to zero and solve for x.

2x - 8 = 0

Add 8 to both sides.

2x = 8

Divide both sides by 2.

x = 4

The rational expression is undefined when x = 4

Check:

Let x = 4, and evaluate the denominator of the fraction.

2x - 8 = 2(4) - 8 = 8 - 8 = 0

By letting x = 4 in the denominator, the denominator does evaluate to zero causing an undefined value in the division. Therefore, our answer above is correct.