# Find the Value of Equation

If a^{3} + b^{3} = 9 and a + b = 3, then the value of 1/a+ 1/b is

- 1/2
- 3/2
- 5/2
- -1

**Answer: (2) 3/2**

**Explanation:-**

(a + b)^{3} = a^{3} + b^{3} + 3ab(a + b)

Put the value of a + b = 3 and a^{3} + b^{3} = 9

Then, 3^{3} = 9 + 3ab(3)

27 – 9 = 9ab

18 = 9ab

ab = 2

Now, 1/a + 1/b = (a + b)/ab

Put the value of a + b = 3 and ab = 2

Then, 3/2Hence, the answer is (2) 3/2.