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Question
If 2x – 1, 5x – 6, 6x + 2 and 15x – 9 are in proportion, find the value of x.
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Solution
∵ 2x – 1, 5x – 6, 6x + 2 and 15x – 9 are in proportion.
then (2x – 1) (15x – 9) = (5x – 6) (6x + 2)
⇒ 30x2 – 18x – 15x + 9
⇒ 30x2 + 10x – 36 - 12
⇒ 30x2 – 33x + 9 = 30x2 – 26x – 12
⇒ 30x2 – 33x – 30x2 + 26x = –12 – 9
⇒ –7 = –21
∴ x = `(-21)/(-7)` = 3
Hence x = 3.
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