คำตอบ - Derivative

Applying the sum rule of derivatives.

$$\frac{d}{dx}[1+3]=\frac{d}{dx}\left[1\right]+\frac{d}{dx}\left[3\right]$$

The derivative of a constant value is always zero.

$$\frac{d}{dx}\left[1\right]+\frac{d}{dx}\left[3\right]=0+\frac{d}{dx}\left[3\right]$$

The derivative of a constant value is always zero.

$$0+\frac{d}{dx}\left[3\right]=0+0$$

Adding zero to a number, which does not change its value.

$$0+0=0$$