Question

if a+b+c=5 and ab+bc+ca=10 then fprove that a power3+ b power 3+ c power 3-3abc =-25

Answer 1

$a+b+c=5$

$ab+bc+ca=10$

Prove That

$a³ + b³ + c³ - 3abc = -25$

$a³ + b³ + c³ - 3abc =  ( a + b + c)(a² + b² + c² - ab - bc - ca)$

$a³ + b³ + c³ - 3abc =  (5)(a² + b² + c² - (ab + bc + ca))$

because $a+b+c=5$

$a³ + b³ + c³ - 3abc =  (5)(a² + b² + c² - (10))$

because $ab+bc+ca=10$

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Now, i don't know.........sorry...........