Question

if a + b + c is equals to 5 and a b + BC + CA is equals to 10 prove that a cube plus b cube plus c cube - 3abc = -25​

Answer 1

Answer:

see below

Step-by-step explanation:

(a+b+c)^3 = a^3 + b^3 + c^3 + 3(a+b+c)(ab+bc+ca) - 3abc

now....

(a+b+c) = 5 ; ab+bc+ca = 10

(5)^3 = a^3 + b^3 + c^3 + 3 × 5 × 10 - 3abc

a^3 + b^3 + c^3 - 3abc = 125 - 150

a^3 + b^3 + c^3 - 3abc = -25

hence proved