RS Aggarwal & V Aggarwal - Mathematics

Book: RS Aggarwal & V Aggarwal - Mathematics

Chapter: 1. Real Number

Subject: Mathematics - Class 9th

Q. No. 40 of CCE Questions

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40

Give an example of two irrational numbers whose sum as well as the product is rational.

Let two irrational numbers be 10 + 2√5 and 5 - 2√5
(i) sum is rational
= 10 + 2√5 + 5 - 2√5


= 15 (a rational number)
(ii) product is rational are


= (10 + 2√5) (10 - 2√5)
= (10)2 - (2√5)2
= 100 - 20 = 80 (a rational number)


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