Derivative of y=(x²+1)³

1. Let $u = x^{2} + 1$.

2. Apply the power rule: $u^{3}$ goes to $3 u^{2}$

3. Then, apply the chain rule. Multiply by $\frac{d}{d x} \left(x^{2} + 1\right)$:

   1. Differentiate $x^{2} + 1$ term by term:

      1. Apply the power rule: $x^{2}$ goes to $2 x$

      2. The derivative of the constant $1$ is zero.

      The result is: $2 x$

   The result of the chain rule is:

   $$6 x \left(x^{2} + 1\right)^{2}$$

4. Now simplify:

   $$6 x \left(x^{2} + 1\right)^{2}$$

The answer is:

$$6 x \left(x^{2} + 1\right)^{2}$$