Question

if a + b + C is equal to 9 and a square + b square + c square is equal to 26 then find the value of a cube plus b cube plus c cube minus 3 ABC​

Answer 1

Given=

a+b+c=9

a²+b²+c²=26

(a+b+c)²=a²+b²+c²+2(ab+bc+ca)

9²=26+2(ab+bc+ca)

81=26+2(ab+bc+ca)

81-26=2(ab+bc+ca)

55=2(ab+bc+ca)

27.5=ab+bc+ca

a³+b³+c³-3abc=

(a+b+c)(a²+b²+c²-(ab+bc+ca)

=9(26-27.5)

=9×-1.5

=-13.5 Ans