Question

If y = 4x – 5 is tangent to the curve y² = px³ + q at (2, 3), then

• A. p = 2, q = – 7
• B. p = –2, q = 7
• C. p = –2, q = –7
• D. p = 2, q = 7

Answer 1

Answer: (A)

p = 2, q = – 7

Answer 2

y = 4x – 5 y² = px³ + q

passes (2, 3)

9 = 8p + q ……(1)

y² = px³ + q, 2y$\frac{dy}{dx}$ = 3px², $\frac{dy}{dx}$ = $\frac{3px^{2}}{2y}$

at(2, 3) = $\frac{3p.4}{6}$= 4, p = 2, q = – 7