Question

9x² + hxy + y² = 0 represents pair of parallel straight lines, if h is ______.

विकल्प

• ±3

• ±6

• ±8

• ±9

Answer 1

9x² + hxy + y² = 0 represents pair of parallel straight lines, if h is ±6.

Explanation:

Comparing the given equation with

Ax² + 2Hxy + By² = 0, we get

A= 9, B = 1 and H = ${\displaystyle \frac{h}{2}}$

Since the lines are parallel,

H² = AB

${\displaystyle \therefore \frac{h^2}{4}=9\left(1\right)}$

⇒ h² = 36

⇒ h = ±6