If 4x2 – 6x + 1 = 0, then the value of 8x3 + 1/(8x3) is?
Show answer & explanation
Correct answer: D
Explanation
Correct Answer is option 4 i.e. 18
|
Concept |
Understanding |
Application |
|
If (a + 1/a) = x (a3 + 1/a3) = x3 – 3x |
Given 4x2 – 6x + 1 = 0
|
4x2 – 6x + 1 = 0 ⇒ 4x2 + 1 = 6x Divide by 2x: ⇒ 2x + 1/2x = 3 Taking cube both sides: ⇒ 8x3 + 1/8x3 + 3 (2x + 1/2x) = 27 ⇒ 8x3 + 1/8x3 + 3 × 3 = 27 ⇒ 8x3 + 1/8x3 = 27 – 9 = 18 |