Find the value of 4-54-5-Is it rational - -3 MARKS-

Concept : 1 Mark Calculation : 2 Marks (4+√(5))(4 √(5))= 4^2 (√(5))^2 nbsp; =16 5=11 [ using the identity nbsp; nbsp;(a+b) (a b)= (a^2 nbsp;b^2)] ...

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Standard XII

Mathematics

Greatest Binomial Coefficients

Find the valu...

Question

Find the value of $(4 + \sqrt{5}) (4 - \sqrt{5})$ .Is it rational ? [3 MARKS]

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Solution

Concept : 1 Mark
Calculation : 2 Marks

$(4 + \sqrt{5}) (4 - \sqrt{5}) = 4^{2} - (\sqrt{5})^{2} = 16 - 5 = 11 [u s i n g t h e i d e n t i t y (a + b) (a - b) = (a^{2} - b^{2})]$

11 is a rational number.

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Find the value of (4+√5)(4−√5).Is it rational ? [3 MARKS]

Concept : 1 Mark Calculation : 2 Marks (4+√5)(4−√5)=42−(√5)2=16−5=11[using the identity (a+b)(a−b)=(a2−b2)] 11 is a rational number.

Find the value of $(4 + \sqrt{5}) (4 - \sqrt{5})$ .Is it rational ? [3 MARKS]

Concept : 1 Mark
Calculation : 2 Marks

$(4 + \sqrt{5}) (4 - \sqrt{5}) = 4^{2} - (\sqrt{5})^{2} = 16 - 5 = 11 [u s i n g t h e i d e n t i t y (a + b) (a - b) = (a^{2} - b^{2})]$

11 is a rational number.