Aptitude | Algebra | Question 2

If x+1/2x = 2, find the value of 8x³+1/x³
(A) 40
(B) 20
(C) 28
(D) 35


Answer: (A)

Explanation:
x³ + 1/8x³ + 3.x.1/2x(x + 1/2x) = (x+1/2x)³

x³ + 1/8x³ + 3 = 2³

x³ + 1/8x³ = 5

8x³ + 1/x³ = 5.8 = 40

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