Sum Cubes Expression
1. **State the problem:** Given $a = \frac{16}{3}$ and $b = \frac{7}{3}$, find the value of $\frac{a^3 + b^3}{a + b} \times ab$.
2. **Recall the algebraic identity:** The sum of cubes factorization is:
$$a^3 + b^3 = (a + b)(a^2 - ab + b^2)$$
3. **Simplify the expression using the identity:**
$$\frac{a^3 + b^3}{a + b} = a^2 - ab + b^2$$
Therefore the original expression becomes
$$\left(a^2 - ab + b^2 \right) \times ab$$
4. **Calculate each element:**
- Calculate $a + b$ (not needed explicitly after step 3).
- Calculate $ab = \frac{16}{3} \times \frac{7}{3} = \frac{112}{9}$.
- Calculate $a^2 = \left(\frac{16}{3}\right)^2 = \frac{256}{9}$.
- Calculate $b^2 = \left(\frac{7}{3}\right)^2 = \frac{49}{9}$.
5. **Substitute into $a^2 - ab + b^2$:**
$$\frac{256}{9} - \frac{112}{9} + \frac{49}{9} = \frac{256 - 112 + 49}{9} = \frac{193}{9}$$
6. **Multiply by $ab$:**
$$\frac{193}{9} \times \frac{112}{9} = \frac{193 \times 112}{81} = \frac{21616}{81}$$
7. **Simplify the fraction if possible:**
Both numerator and denominator divisible by 1 only, so final simplified value is
$$\frac{21616}{81}$$
**Final answer:**
$$\frac{21616}{81}$$