# a3+b3=9 and a+b=3 then the value of 1/a+1/b is

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

**Solution:-**

a^3 + b^3 = 9 …………………….. (1)

And a +b = 3 ………………… (2)

Now,

a + b = 3

Cube on both side,

(a + b)^3 = 3^3

a^3 + b^3 + 3 a b (a + b) = 3 x 3 x 3

From equation (1) & (2)

9 + 3 a b x 3 = 27

9 ab = 27 – 9

9 ab = 18

ab = 18/9

ab = 2 …………………….. (3)

Then,

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

From equation (2) & (3)

(a + b)/ab = 3/2

Then, the value of 1/a + 1/b is 3/2.

Hence, the correct answer is option (b) 3/2.