Question

If a+b=6 & a square +b square =20 . find a cube + b cube

Answer 1

a=2

b=4

So,a cube =8 +b cube = 64

Answer=72

Answer 2

Answer:

a³ + b³ = 162

Step-by-step explanation:

a³ + b³ = (a + b)³ - 3ab(a+b)

a² + b² = 20

a +b = 6

Squaring both sides

(a +b)² = 6²

=> a² + b² + 2ab = 26

=> 20 + 2ab = 26

=> 2ab = 6

=> ab = 3

now

a³ + b³ = (a + b)³ - 3ab(a+b)

=> a³ + b³ = 6³ -3×(3)×(6)

=> a³ + b³ = 216 - 54

=> a³ + b³ = 162