harder 3 Unit Inequalities question (1 Viewer)

[asianese]

Actually with the AM-GM inequality you should not just assume it but prove it before hand. The questions like this should be made so that you are made to prove it before anyway but still...

They're all quite simple - provided you don't take the long arguous route for the 3VAR case.


Also questions like the one above are quite standard inequalities. You should memorise such simpler proofs - obviously with knowing what's going on.

 

[ihave2shadows]

Another method to prove
1/a + 1/b + 1/c >= 9 is to show a+1/a>=2 and similarly a/b+1/(a/b)>=2
(1/a + 1/b + 1/c)(a+b+c)=a/a+a/b+a/c+a/b+b/b+b/c+c/a+b/c+c/c>=3+2+2+2>=9