Correct Answer - Option 4 : 4
Given:
√(7 + 2√12) – [1/√(7 – 2√12)]
Concept used:
(a + b)2 = a2 + b2 + 2ab
Calculation:
(7 + 2√12) = 3 + 4 + 2√3 × √4
⇒ (7 + 2√12) = (√3 + √4)2
√(7 + 2√12) = (√3 + √4)
(7 – 2√12) = 3 + 4 – 2√3 × √4
⇒ (7 – 2√12) = (√4 – √3)2
√(7 – 2√12) = (√4 – √3)
√(7 + 2√12) – [1/√(7 – 2√12)]
⇒ (√3 + √4) – [1/(√4 – √3)]
⇒ (√3 + √4) – [1/(√4 – √3)] × [(√3 + √4)/(√3 + √4)]
⇒ (√3 + √4) – (√3 + √4)
⇒ 0
∴ The required value is 4.