Derivative as a Gradient Function

Derivative as a Gradient Function

The derivative \(\mathrm{f}^{\prime}(x)\) gives the tangent gradient where the curve is differentiable.

\(\dfrac{\mathrm{d}y}{\mathrm{d}x}=\mathrm{f}^{\prime}(x)\qquad\dfrac{\mathrm{d}}{\mathrm{d}x}(x^n)=nx^{n-1}\)

Apply the power rule where the function and derivative exist. Rewrite roots and reciprocals as powers first.

For a straight line, the gradient is \(\dfrac{y_2-y_1}{x_2-x_1}\): vertical change divided by horizontal change.

Example

For \(y=3\), the gradient is \(0\). For both \(y=2x\) and \(y=2x-3\), the gradient is \(2\).

For \(y=x^2\), the gradient depends on the point on the curve.

\(\dfrac{\mathrm{d}y}{\mathrm{d}x}\)\({}=2x\)

At \(x=-1,0,1,2\), the gradients are respectively \(-2,0,2,4\). At \(x=a\), the gradient is \(2a\).

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Answer:\(y=3\mapsto0\), \(y=2x\mapsto2\), \(y=2x-3\mapsto2\), \(y=x^2\mapsto2x\)

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