Rationalizing the Denominator






In this page rationalizing the denominator we are going to see some examples to show that how to rationalize the denominator in fraction.

Definition:

Some times the denominator of a ratio a/b may be a surd. In those ratios, the denominator can be made a rational number by common procedure. This procedure is known as rationalizing the denominator.


If the denominator is as follows



Procedure


(1) If the denominator is in the form

of √a where a is a rational number.

Then we have to multiply

both the numerator and

denominator by the same

(√a). For example

Explanation:

In this question we have √5 in the denominator since it is rational we have to multiply the same with the numerator and denominator to rationalize the given fraction. So that we are getting  √15/5

(2) If the denominator is in the form

of a + √b where a and b are rational

numbers.

Then we have to multiply

both the numerator and

denominator by its

conjugate (a - √b). For

example

Explanation:

In this question we have 3 + √5 in the denominator so we have to multiply by its conjugate that is 3 - √5  with both numerator and denominator. Now the denominator is like in the form (a+ b) (a-b). So we have simplified this using a² - b².By simplifying this we get (3-√5)/2 as answer.

(3) If the denominator is in the form

of a - √b where a and b are rational

numbers.

Then we have to multiply

both the numerator and

denominator by its

conjugate (a + √b). For

example

Explanation:

In this question we have 3 - √2 in the denominator so we have to multiply by its conjugate that is 3 + √2  with both numerator and denominator. Now the denominator is like in the form (a+b) (a-b). So we have simplified this using a² - b².By simplifying this we get (15+5√2)/7 as answer.

(4) If the denominator is in the form

of √a + √b where a and b are

rational numbers.

Then we have to multiply

both the numerator and

denominator by its

conjugate (√a - √b). For

example

Explanation:

In this question we have √2 + √5 in the denominator so we have to multiply by its conjugate that is √2 - √5  with both numerator and denominator. Now the denominator is like in the form (a+b) (a-b). So we have simplified this using a² - b².By simplifying this we get (2√5-2√2)/3 as answer.


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