Question

If a+b+c = 5 and ab+bc+ca = 10 , Then prove that a³+b³+c³ -3abc = -25 .

Answer 1

if a+b+c=5 and ab+bc+ca=10

a^3+b^3+c^3 -3abc = -25
5^3+5^3+5^3 -3×10+10+10 =-25
125+125+125-3×30=-25
375-90=-25
285=-25
= -25/285
=-5/57