When do you need to rationalize the denominator? my physics teacher says that you don't have to if you are isolating a variable.

When the denominator is an irrational number in order to make the denominator a rational number we rationalize the denominator.

Step-by-step explanation:

For example,

(here the denominator is an irrational number)

Multiply the numerator and denominator by

We get

Here (1+\sqrt{2})(1-\sqrt{2}) = -1

Thus we get

Here the denominator has become a rational number.

When we are isolating a variable we are only taking the required variables to one side thus it doesn't require rationalization.

Then we can say,

No rationalisation required

answer: 20

step-by-step explanation: