The Derivative of xⁿ (Short-Hand Differentiation)

Observe the pattern of the following table.

𝑓(𝑥)𝑓(𝑥)
𝑓(𝑥)=𝑥𝑓(𝑥)=1𝑥0=1
𝑓(𝑥)=𝑥2𝑓(𝑥)=2𝑥1=2𝑥
𝑓(𝑥)=𝑥3𝑓(𝑥)=3𝑥2
𝑓(𝑥)=𝑥4𝑓(𝑥)=4𝑥3
𝑓(𝑥)=𝑥5𝑓(𝑥)=5𝑥4

We can see that the power of 𝑓(𝑥) is multiplied onto 𝑥. The power of 𝑓(𝑥) also decreases by 1. So, therefore:

𝑚=𝑛𝑥𝑛1

For Certain Functions

For linear functions (𝑦=𝑚𝑥+𝑐), 𝑑𝑦𝑑𝑥=𝑚.
For horizontal lines (𝑦=𝑘), 𝑑𝑦𝑑𝑥=0.

Tip

In regards to other types of functions… (generalised)

For𝑦=𝑥𝑛, 𝑑𝑦𝑑𝑥=𝑛𝑥𝑛1For𝑦=𝑘𝑥𝑛, 𝑑𝑦𝑑𝑥=𝑘𝑛𝑥𝑛1For𝑦=𝑘𝑓(𝑥), 𝑑𝑦𝑑𝑥=𝑘𝑓(𝑥)For𝑦=𝑓(𝑥)+𝑔(𝑥), 𝑑𝑦𝑑𝑥=𝑓(𝑥)+𝑔(𝑥)For𝑦=𝑥𝑛+𝑐,𝑑𝑦𝑑𝑥=𝑛𝑥𝑛1+0

Equation of the Tangent

The equation of the tangent is derived from the linear function (𝑓(𝑥)=𝑚𝑥+𝑐), with 𝑚=𝑓(𝑥) at that point where the tangent is present.

Example

Let 𝑓(𝑥)=𝑥2, 𝑓(𝑥)=2𝑥.

If a tangent line was drawn at 𝑥=1, the gradient of the tangent at 𝑥=1 would be 𝑓(1). 𝑓(1)=2(1)=2.

Thus, the equation of the tangent would be (with the substitution of 𝑓(1), which equals 𝑚), is 𝑦=2𝑥+𝑐.