1. **State the problem:** We want to solve the integral $$\int (4x^2 - 12x + 9)^{\frac{2}{3}} \, dx$$ using substitution.
2. **Identify substitution:** Notice the expression inside the parentheses is a quadratic. Let's try to simplify it by completing the square:
$$4x^2 - 12x + 9 = (2x)^2 - 2 \cdot 2x \cdot 3 + 3^2 = (2x - 3)^2$$
3. **Rewrite the integral:**
$$\int (4x^2 - 12x + 9)^{\frac{2}{3}} \, dx = \int ((2x - 3)^2)^{\frac{2}{3}} \, dx = \int (2x - 3)^{\frac{4}{3}} \, dx$$
4. **Use substitution:** Let
$$u = 2x - 3$$
Then,
$$\frac{du}{dx} = 2 \implies dx = \frac{du}{2}$$
5. **Rewrite integral in terms of $u$:**
$$\int (2x - 3)^{\frac{4}{3}} \, dx = \int u^{\frac{4}{3}} \cdot \frac{du}{2} = \frac{1}{2} \int u^{\frac{4}{3}} \, du$$
6. **Integrate:** Use the power rule for integrals:
$$\int u^n \, du = \frac{u^{n+1}}{n+1} + C$$
Here, $n = \frac{4}{3}$, so
$$\int u^{\frac{4}{3}} \, du = \frac{u^{\frac{4}{3} + 1}}{\frac{4}{3} + 1} + C = \frac{u^{\frac{7}{3}}}{\frac{7}{3}} + C = \frac{3}{7} u^{\frac{7}{3}} + C$$
7. **Substitute back:**
$$\frac{1}{2} \int u^{\frac{4}{3}} \, du = \frac{1}{2} \cdot \frac{3}{7} u^{\frac{7}{3}} + C = \frac{3}{14} (2x - 3)^{\frac{7}{3}} + C$$
**Final answer:**
$$\int (4x^2 - 12x + 9)^{\frac{2}{3}} \, dx = \frac{3}{14} (2x - 3)^{\frac{7}{3}} + C$$
Integral U Substitution 15311A
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