The derivative of x² is 2x:

$$\frac{d}{dx} \left( x^2 \right) = 2x$$

To calculate the derivative of $x^2$, you apply the power rule from calculus. The power rule states:

$$\frac{d}{dx} \left( x^n \right) = n x^{n-1}$$

For $x^2$:

1. Identify $n = 2$.
2. Apply the power rule: Multiply by the exponent $n$, then reduce the power by 1.

$$\frac{d}{dx} \left( x^2 \right) = 2x^{2-1} = 2x$$

So, the derivative of $x^2$ is $2x$.