Saturday, 30 January 2016

taylor expansion - Proof an inequality



I'm trying to prove that
32115m21+12m21+3m2



I have obtained in a CAS software the Taylor expansion in m=0
enter image description here




One posibility to prove the inequality is showing coeficients in Taylor expansion are non-negative, by I don't find how.



Really I want only to obtain inequality. Some idea?



EDIT



m must be between $0

Answer



32115m21+12m21+3m2
32115m2(1+3m2)(1+12m2)

2115m23(1+3m2)(1+12m2)
115m23(1+3m2)(1+12m2)2
115m2215m236m42
Note that on the interval you're concerned about, the right hand side is always positive. Proof: it's obviously decreasing on (0,115), and is equal to 2150 at the right endpoint. Therefore squaring both sides is legal here with an statement.
115m2215m236m42
115m2(215m236m42)2
115m2324m8+270m6+814m415m2+1
0324m8+270m6+814m4



This last statement is clearly true.



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