Question

Which of the following pair of straight lines intersect at right angles?

Options

• 2x² = y(x + 2y)

• (x + y)² = x(y + 3x)

• 2y(x + y) = xy

• y = ± 2x

Answer 1

2x² = y(x + 2y)

Explanation:

Condition for pair of straight lines given by ax² + 2hxy + by² = 0 to be mutually perpendicular is a+ b = 0.

This condition is satisfied by the equation given in option (A), i.e.,

2x² = y(x + 2y)

⇒ 2x² - xy - 2y² = 0

⇒ a + b = 2 + (- 2) = 0