Integral Function
1. The problem states that $$\int (f(x))^n \cdot g(x) \, dx = \frac{1}{n+1} [f(x)]^{n+1} + c$$.
2. To find $$g(x)$$, differentiate both sides with respect to $$x$$ using the Fundamental Theorem of Calculus:
$$\frac{d}{dx} \left( \int (f(x))^n \cdot g(x) \, dx \right) = \frac{d}{dx} \left( \frac{1}{n+1} [f(x)]^{n+1} + c \right)$$
3. The left side simplifies to:
$$(f(x))^n \cdot g(x)$$
4. The right side differentiates as:
$$\frac{1}{n+1} \cdot (n+1) [f(x)]^n \cdot f'(x) = [f(x)]^n \cdot f'(x)$$
5. Equate both sides:
$$(f(x))^n \cdot g(x) = (f(x))^n \cdot f'(x)$$
6. Since $$ (f(x))^n \neq 0 $$, divide both sides by $$ (f(x))^n $$:
$$g(x) = f'(x)$$
7. Therefore, the correct answer is (b) $$f'(x)$$.
Final answer: $$g(x) = f'(x)$$.