Question

If a+b=3 and ab =2 , then find the value of a cube + b cube

Answer 1

a^3 + b^3 = (a+b)(a^2 + b^2 - ab)

To find a^2 + b^2 :

(a+b)^2 = a^2 + b^2 +2ab
3^2 = a^2 + b^2 + 2×2
9 - 4 = a^2 + b^2
a^2 + b^2 = 5

Now,
3 × (5-2)
3 × 3
9