- #1
penguin007
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Homework Statement
Hi everyone,
I'm trying to proove that for x real, ln(1+x)<=x
Homework Equations
The Attempt at a Solution
I know that I can solve this problem by introducing f:=x->ln(1+x)-x and studying f, but I'd like to use x->ln(1+x)'s concavity so I tried to find lambda, x and y in :
ln(1+(lambda)*x+(1-lambda)*y)>=(lambda)*ln(1+x)+(1-lambda)*ln(1+y)...
Any help is welcome...