Question

X+1/X=√5,ആയാൽ X³+1/ X³=?

• A. 10√5
• B. 2√5
• C. 5√5
• D. None of these

Answer 1

Answer:

B. 2√5

X+1/X=√5 a³ + b³ = (a + b)³ - 3ab(a + b) X³ + 1/ X³ = (X+1/X)³ - 3X × 1/X × (X+1/X) = (X+1/X)³ - 3(X+1/X) = (√5)³ - 3(√5) = 5√5 - 3√5 = 2√5