Question

(a/b)³+( b/c³)+(c/a³)-3​

Answer 1

1

Secondary School Math 5 points

Prove that ( a+b+c ) ³ -a³-b³-c³ = 3 ( a+ b ) ( b+ c ) (c+a)

Ask for details Follow Report by Ishitarana11 12.09.2016

Answers

ARoy

ARoy Expert

(a+b+c)³-a³-b³-c³

=(a+b)³+3(a+b)²c+3(a+b)c²+c³-a³-b³-c³

=a³+3a²b+3ab²+b³+3(a²+2ab+b²)c+3ac²+3bc²+c³-a³-b³-c³

=3a²b+3ab²+3a²c+6abc+3b²c+3ac²+3bc²

=3(2abc+a²b+ab²+a²c+ac²+b²c+bc²)

3(a+b)(b+c)(c+a)

=3(ab+b²+ac+bc)(c+a)

=3(abc+b²c+ac²+bc²+a²b+ab²+a²c+abc)

=3(2abc+a²b+ab²+a²c+ac²+b²c+bc²)

∴, LHS=RHS (Proved)