Question

Which of the following is not an irrational number? निम्नलिखित में से कौन सी एक अपरिमेय संख्या नहीं है? *

5+ √5

(2+ √5 )√5

(2 + √5 )(2 - √5)

5√5

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Answer 1

$\huge{\boxed{\red{Let's \:check:}}}$

• 5+ √5 is is irrational

$Why?$

Because √5 cannot be written in form fraction

• (2+ √5 )√5 =2√5+5 =√10+5 is irrational

$Why?$

Because √10 can not be written in form of fraction

• (2 + √5 )(2 - √5)

=2²-(√5)²

=4-5

=-1 is rational✓

$Why?$

because it can be written in fraction

eg:

-1/1

• 5√5 =√10 is irrational

$Why?$

The square root of 2 cannot be written as a simple fraction.And therefore √10 is irrational number.

So option 3 is correct

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Answer 2

Answer:

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