Question

The straight lines of the family x(a + b) + y (a – b) = 2a

(a and b being parameters) are

• A. Not concurrent
• B. Concurrent at (1, -1)
• C. Concurrent at (1, 1)
• D. None of these

Answer 1

Answer: (C)

Concurrent at (1, 1)

Answer 2

The given equation can be written as

a(x + y –2) + b(x–y) = 0

or (x+y–2) + b/a (x-y) = 0.

This is a family of lines concurrent at x-y = 0 and x+y –2 = 0.

On solving these two equations we get (1, 1)