Question

Find the value of ‘a’ for which the straight lines 3x + 4y = 13; 2x – 7y = -1 and ax – y – 14 = 0 are concurrent.

Answer 1

The lines 3x + 4y = 13, 2x – 7y = -1 and ax – y – 14 = 0 are concurrent.

`|(3,4,-13),(2,-7,1),(a,-1,-14)| = 0`

⇒ 3(98 + 1) – 4(-28 – a) – 13(-2 + 7a) = 0

⇒ 3(99) + 112 + 4a + 26 – 91a = 0

⇒ 297 + 112 + 26 + 4a – 91a = 0

⇒ 435 – 87a = 0

⇒ - 87a = -435

⇒ a = `(- 435)/(- 87)` = 0