What Is Rationalizing the Denominator?
Rationalizing the denominator means rewriting a fraction so that its bottom no longer contains a radical (square root), typically by multiplying both the numerator and denominator by a value that clears the root out of the denominator. The value of the fraction doesn't change, only its form, since multiplying by a fraction equal to 1 never changes the result.
Example
1/√2 is rationalized by multiplying top and bottom by √2, giving (1×√2)/(√2×√2) = √2/2.