The value of 1/(9 - 4 √(5))2 + 1/(9 + 4 √(5))2 is:
Show answer & explanation
Correct answer: D
Explanation
The correct answer is option 4 i.e 322
We know that 1 / (a - √b) = a + √b
By this property, we will proceed as
⇒ 1/(9 - 4 √(5))2 + 1/(9 + 4 √(5))2
⇒ (9 + 4 √(5))2 + (9 - 4 √(5))2
⇒ 2(92 + (4√(5)2)
⇒ 2 × 162 = 322