Question

if a+b=10,ab=21.then a cube+b cube=

Answer 1

a+b= 10
ab= 21
a3+b3= (a+b) (a2+b2-ab)

(a+b)2= a2+b2+2ab
10^2= a2+b2+2x21
100= a2+b2+42
100-42= a2+b2
a2+b2= 58

a3+b3= 10x 58-(21)
a3+b3= 10x 37
a3+b3= 370

Answer 2

a+b = 10 and ab = 21

a³+b³ = (a+b)³ - 3a²b-3ab²

→ (10)³ - 3ab(a+b)

→ 10³ - 3(21)(10)

→ 1000-630

→ 370

Hope it helps