Define function f(x) as:
f(x)=2x2+ln(1+x)−x
Note that: f(0)=0
Let us find first derivative of function f(x) :
f′(x)=x+1x2 ,
Note that f′(x)>0 for all x>0
Since f(0)=0 and f′(x)>0 for all x>0 it follows that:
2x2+ln(1+x)−x>0⇒ln(1+x)>x−2x2 , for all x>0
Hence Proved.
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