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Category: Relation and Functions

Find-all-polynomials-P-x-with-real-coefficients-such-that-for-all-nonzero-real-numbers-x-P-x-P-1-x-P-x-1-x-P-x-1-x-2-

Question Number 200722 by cortano12 last updated on 22/Nov/23 $$\:\:\mathrm{Find}\:\mathrm{all}\:\mathrm{polynomials}\:\mathrm{P}\left(\mathrm{x}\right)\:\mathrm{with} \\ $$$$\:\mathrm{real}\:\mathrm{coefficients}\:\mathrm{such}\:\mathrm{that}\:\mathrm{for} \\ $$$$\:\mathrm{all}\:\mathrm{nonzero}\:\mathrm{real}\:\mathrm{numbers}\:\mathrm{x},\: \\ $$$$\:\:\:\:\:\mathrm{P}\left(\mathrm{x}\right)+\mathrm{P}\left(\frac{\mathrm{1}}{\mathrm{x}}\right)=\frac{\mathrm{P}\left(\mathrm{x}+\frac{\mathrm{1}}{\mathrm{x}}\right)+\mathrm{P}\left(\mathrm{x}−\frac{\mathrm{1}}{\mathrm{x}}\right)}{\mathrm{2}}\:\:\: \\ $$ Commented by Frix last updated on 22/Nov/23…

Question-199781

Question Number 199781 by cortano12 last updated on 09/Nov/23 $$\:\:\: \\ $$ Answered by qaz last updated on 09/Nov/23 $${f}\left({x}\right)=\frac{\mathrm{2}\left(\mathrm{1}−\mathrm{2}{x}\right)}{{x}\left(\mathrm{1}−{x}\right)}−{f}\left(\frac{\mathrm{1}}{\mathrm{1}−{x}}\right) \\ $$$$=\frac{\mathrm{2}\left(\mathrm{1}−\mathrm{2}{x}\right)}{{x}\left(\mathrm{1}−{x}\right)}−\left(\frac{\mathrm{2}\left(\mathrm{1}−\frac{\mathrm{2}}{\mathrm{1}−{x}}\right)}{\frac{\mathrm{1}}{\mathrm{1}−{x}}\left(\mathrm{1}−\frac{\mathrm{1}}{\mathrm{1}−{x}}\right)}−{f}\left(\frac{\mathrm{1}}{\mathrm{1}−\frac{\mathrm{1}}{\mathrm{1}−{x}}}\right)\right) \\ $$$$=\frac{\mathrm{2}\left(\mathrm{1}−\mathrm{2}{x}\right)}{{x}\left(\mathrm{1}−{x}\right)}−\frac{\mathrm{2}\left(\mathrm{1}+{x}\right)\left(\mathrm{1}−{x}\right)}{{x}}+{f}\left(\mathrm{1}−\frac{\mathrm{1}}{{x}}\right) \\…

Give-a-function-f-R-0-continous-on-R-and-such-that-f-x-y-f-x-f-y-a-Prove-f-0-1-b-Let-h-x-ln-f-x-Prove-that-h-x-y-h-x-h-y-c-Find-all-the-function-f-such-that-problem-re

Question Number 199167 by tri26112004 last updated on 28/Oct/23 $${Give}\:{a}\:{function}\: \\ $$$${f}:\:{R}\rightarrow\left(\mathrm{0};+\infty\right)\:{continous}\:{on}\:{R}\:{and}\:{such}\:{that} \\ $$$${f}\left({x}+{y}\right)\:=\:{f}\left({x}\right).{f}\left({y}\right) \\ $$$${a}.\:{Prove}\:{f}\left(\mathrm{0}\right)\:=\:\mathrm{1} \\ $$$${b}.\:{Let}\:{h}\left({x}\right)\:=\:{ln}\left[{f}\left({x}\right)\right].\:{Prove}\:{that}: \\ $$$$\:{h}\left({x}+{y}\right)\:=\:{h}\left({x}\right)\:+\:{h}\left({y}\right) \\ $$$${c}.\:{Find}\:{all}\:{the}\:{function}\:{f}\:{such}\:{that}\:{problem}\:{request} \\ $$$$\:\:\: \\…

if-f-x-is-also-differentiable-on-R-such-that-f-x-gt-f-x-x-R-and-f-x-0-0-then-prove-that-f-x-0-x-gt-x-0-

Question Number 198279 by universe last updated on 16/Oct/23 $$\:\:\mathrm{if}\:\mathrm{f}\left(\mathrm{x}\right)\:\mathrm{is}\:\mathrm{also}\:\mathrm{differentiable}\:\mathrm{on}\:\mathbb{R}\:\mathrm{such}\:\mathrm{that} \\ $$$$\:\:\mathrm{f}'\left(\mathrm{x}\right)\:>\:\mathrm{f}\left(\mathrm{x}\right)\:\forall\:\mathrm{x}\:\in\:\mathbb{R}\:{and}\:\mathrm{f}\left(\mathrm{x}_{\mathrm{0}} \right)\:=\:\mathrm{0}\:\mathrm{then}\: \\ $$$$\:\:\mathrm{prove}\:\mathrm{that}\:\:\mathrm{f}\left(\mathrm{x}\right)\:\geqslant\:\mathrm{0}\:\forall\:\mathrm{x}\:>\:\mathrm{x}_{\mathrm{0}} \\ $$ Answered by witcher3 last updated on 16/Oct/23 $$\mathrm{f}'\left(\mathrm{x}\right)−\mathrm{f}\left(\mathrm{x}\right)>\mathrm{0}….\left(\mathrm{1}\right)…

2-x-9-2-x-40-

Question Number 198065 by giovi last updated on 09/Oct/23 $$\mathrm{2}^{{x}} +\mathrm{9}+\mathrm{2}^{{x}} =\mathrm{40} \\ $$ Answered by a.lgnaoui last updated on 09/Oct/23 $$\:\mathrm{2}^{\mathrm{x}+\mathrm{1}} =\mathrm{31}\Rightarrow\:\:\left(\:\mathrm{x}+\mathrm{1}\right)\mathrm{ln2}=\mathrm{ln31} \\ $$$$\:\:\mathrm{x}=\frac{\mathrm{ln31}}{\mathrm{ln2}}−\mathrm{1}\:\:\:\:\:\:\:\:\:\boldsymbol{\mathrm{x}}=\frac{\boldsymbol{\mathrm{ln}}\mathrm{31}−\boldsymbol{\mathrm{ln}}\mathrm{2}}{\boldsymbol{\mathrm{ln}}\mathrm{2}}…