Question

The point at which the tangent to the curve y = x³ + 5 is perpendicular to the line x + 3y = 2 are –

• A. (1, 6), (1, 4)
• B. (1, 6), (–1, 4)
• C. (6, 1), (–1, 4)
• D. (6, 1) (4, –1)

Answer 1

Answer: (B)

(1, 6), (–1, 4)

Answer 2

Slope of line = m₁ = –1/3

m₂ = Slope of tangent $\left( \frac{dy}{dx} \right)$=3x² Ž m₁ × m₂ = –1

Ž 3x² × (–1/3) = – 1

x² = 1 Ž x = 1, x = – 1 & y = 6, y = 4