If (7x + 3)3 + (x - 2)3 + 27(2x-5)3 = 9(7x + 3) (x-2) (2x-5), then the value of 5x + 3 is
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Correct answer: D
Explanation
The correct answer is option 4 i.e. 8.
(7x + 3)3 + (x - 2)3 + 33(2x - 5)3 = 3 × (7x + 3) × (x - 2) × 3(2x - 5)
If a3 + b3 + c3 = 3abc then a + b + c = 0
⇒ (7x + 3) + (x - 2) + 3(2x - 5) = 0
⇒ 7x + 3 + x - 2 + 6x - 15 = 0
⇒ 14x - 14 = 0
⇒ x = 1
Then,
⇒ 5x + 3 = 5 × 1 + 3 = 8
5x + 3 = 8