Question

if a-b=7 a²+b²=84 a³-b³=?

Answer 1

If a-b=7,a²+b²=84 find a³-b³

a-b = 7 ; a²+b² = 84

(a-b)² = a²+b²-2ab
(7)² = 84-2ab
2ab = 84-49
2ab = 35
ab = 35/2
ab = 17.5

a³−b³ =(a−b)³ +3ab(a−b)
= (7)³+3(17.5)(7)
= 343 + 367.5
= 710.5