Question

If the line ax + by + c = 0 is a tangent to the curve xy + 2 = 0 then

• A. a > 0, b > 0
• B. a > 0, b < 0
• C. a > 0, c > 0
• D. a > 0, c < 0

Answer 1

Answer: (B)

a > 0, b < 0

Answer 2

For xy = −2, $\frac { d y } { d x } = \frac { 2 } { x ^ { 2 } }$ which is always positive.

Thus > 0 or signs of 'a' and 'b' must be opposite.