Differentiation - Tangents and Normals at a Point

Differentiation - Tangents and Normals at a Point

Secondary 4

It is given that \(\mathrm{f}(x) = \frac{1}{3}x^3 + 2x^2 - 5x\).

\(\mathrm{f}(x)\) has a maximum point at \(M\), and a point of inflexion at \(N\).

  1. Find \(\mathrm{f}'(x)\).
  2. Find the \(x\)-coordinate of \(M\).
  3. Find the \(x\)-coordinate of \(N\).
  4. The line \(L\) is the tangent to the curve of \(\mathrm{f}\) at \((3, 12)\).
    Find the equation of \(L\) in the form \(y = ax + b\).
Answer:(a) \(\mathrm{f}\,\text{}\hspace{0.5em}\!\!'\!\!\text{}\hspace{0.5em}\left( x \right)={{x}^{2}}+4x-5\) (b) \(x=-5\) (c) \(x=-2\) (d) \(y=16x-36\)

Need help? Join our A-Maths tuition classes.

Learn more