Question

If 2x – 1, 5x – 6, 6x + 2 and 15x – 9 are in proportion, find the value of x.

Answer 1

∵ 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.