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Differentiation practice questions

To differentiate using the power rule, multiply by the power then reduce the power by one, so a x to the n becomes a n x to the n minus one. For y equals 4x cubed, the derivative is 12x squared. Substitute an x value into the derivative to find the gradient there.

Differentiation finds the rate of change of a function, and the gradient of a curve at any point. The power rule handles most A-level Pure questions: multiply by the power, then reduce the power by one.

A-level

The method, step by step

  1. Apply the power rule. For axn, the derivative is anxn−1.
  2. Differentiate term by term. Each term is handled independently.
  3. Constants vanish. The derivative of any number on its own is 0.
  4. Substitute for a gradient. To find the gradient at a point, substitute the x value into the derivative.

Worked example

Differentiate y = 4x³ and find the gradient at x = 2
Multiply by the power and reduce it: 4 × 3 = 12, and the power drops to 2.
So dy/dx = 12x².
Substitute x = 2: 12 × 4 = 48.
dy/dx = 12x², and the gradient at x = 2 is 48

Common mistakes

Reducing the power without multiplying by it first.

Differentiating a constant into itself rather than 0.

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