Question

If a+b+c =5 and ab+ bc +ca 10 then prove that a square + b square + c square =-25

Answer 1

(a + b + c)² = a² + b² + c² + 2 (ab+bc+ac)

5² = a² + b² + c² + 2x 10

25 = a² + b² + c² +20

a² + b² + c²  = 25 - 5 =5

Sorry question is wrong somewhere. this answer -25 will come only if the question is a³ + b³ + c³ - 3abc