Prove that (a+b+c)^3-a^3-b^3-c^3=3(a+b)(b+c)(c+a)
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Step-by-step explanation:
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Answered by
1
Step-by-step explanation:
(a+b+c)³=[a+(b+c)]³
=a³+(b+c)³+3a(b+c)[a+(b+c)]
=a³+b³+c³+3bc(b+c)+3a(b+c)[a+(b+c)]
=a³+b³+c³+3(b+c)[bc+a{a+(b+c)}]
=a³+b³+c³+3(b+c)[bc+a²+ab+ac]
=a³+b³+c³+3(b+c)[a(a+b)+c(a+b)]
=a³+b³+c³+3(b+c)(a+c)(a+b)
(a+b+c)³-a³-b³-c³=3(a+b)(b+c)(c+a)
hence, proved
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