x2 = 11 + 2√30 হলে, 1/x এর মান কত?

A √3 - √2

B √5 - √4

C √7 - √6

D √6 - √5

Solution

Correct Answer: Option D

দেওয়া আছে,
বা, x2 = 11 + 2√30
বা, x2 = 6 + 2√30  + 5
বা, x2 = (√6)2 + 2.√6.√5 + (√5)2
বা, x2 = (√6 + √5)2
বা, x = √6 + √5
 
1/x
= 1/(√6 + √5)
= (√6 - √5)/ (√6 + √5) (√6 - √5)
=  (√6 - √5)/ {(√6)2 - (√5)2}
= (√6 - √5)/(6 - 5)
= √6 - √5

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