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Category: Arithmetic

Question-94298

Question Number 94298 by peter frank last updated on 17/May/20 Answered by Ar Brandon last updated on 18/May/20 $$\mathrm{log}_{\mathrm{2}} \left(\mathrm{1}×\mathrm{2}×\mathrm{3}×…×\mathrm{n}\right)=\mathrm{1994} \\ $$$$\mathrm{log}_{\mathrm{2}} \left(\mathrm{n}!\right)=\mathrm{1994}\Rightarrow\mathrm{n}!=\mathrm{2}^{\mathrm{1994}} \\ $$$$\mathrm{n}\approx\mathrm{295}…

Question-94297

Question Number 94297 by peter frank last updated on 17/May/20 Commented by mathmax by abdo last updated on 18/May/20 $${we}\:{know}\:{that}\:{x}^{\mathrm{2}} \:+{y}^{\mathrm{2}} \:+{z}^{\mathrm{2}} =\mathrm{0}\:\Rightarrow{x}={y}={z}\:\:\:\left({for}\:{x},{y}\:,{z}\:{reals}\right) \\ $$$${so}\:\left({e}\right)\:\Rightarrow{cosx}\:={cos}\left(\mathrm{2}{x}\right)={cos}\left(\mathrm{3}{x}\right)=\mathrm{0}…

Prove-that-689-690-691-1-is-a-naturel-number-

Question Number 159750 by greg_ed last updated on 20/Nov/21 $$\boldsymbol{\mathrm{Prove}}\:\boldsymbol{\mathrm{that}}\: \\ $$$$\:\sqrt{\mathrm{689}×\mathrm{690}×\mathrm{691}+\mathrm{1}}\:\boldsymbol{\mathrm{is}}\:\boldsymbol{\mathrm{a}}\:\boldsymbol{\mathrm{naturel}}\:\boldsymbol{\mathrm{number}}. \\ $$ Commented by Rasheed.Sindhi last updated on 20/Nov/21 $${Pl}\:{check}\:{the}\:{question},\:\sqrt{\mathrm{689}×\mathrm{690}×\mathrm{691}+\mathrm{1}}\: \\ $$$${is}\:{not}\:{a}\:{natural}\:{number}. \\…

find-all-integers-n-for-which-13-4-n-2-1-

Question Number 94097 by Rio Michael last updated on 16/May/20 $$\mathrm{find}\:\mathrm{all}\:\mathrm{integers}\:{n}\:\:\mathrm{for}\:\mathrm{which}\:\:\mathrm{13}\:\mid\mathrm{4}\left({n}^{\mathrm{2}} +\mathrm{1}\right). \\ $$ Commented by Rasheed.Sindhi last updated on 17/May/20 $${This}\:{s}\:{equivalent}\:{to}: \\ $$$$\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\mathrm{13}\:\mid\left({n}^{\mathrm{2}} +\mathrm{1}\right)…

Question-28449

Question Number 28449 by A1B1C1D1 last updated on 25/Jan/18 Answered by $@ty@m last updated on 26/Jan/18 $${there}\:{are}\:{infinitely}\:{many}\:{solutions}: \\ $$$$\left(\mathrm{0},\pm\mathrm{1}\right) \\ $$$$\left(\pm\mathrm{1},\mathrm{0}\right) \\ $$$$\left(\pm\frac{\mathrm{3}}{\mathrm{5}},\pm\frac{\mathrm{4}}{\mathrm{5}}\right) \\ $$$$\left(\pm\frac{\mathrm{5}}{\mathrm{13}},\pm\frac{\mathrm{12}}{\mathrm{13}}\right)…

n-1-1-n-n-1-

Question Number 93859 by  M±th+et+s last updated on 15/May/20 $$\underset{{n}=\mathrm{1}} {\overset{\infty} {\sum}}\:\frac{\mathrm{1}}{{n}\left({n}+\mathrm{1}\right)} \\ $$ Answered by Ar Brandon last updated on 15/May/20 $$\frac{\mathrm{1}}{\mathrm{n}\left(\mathrm{n}+\mathrm{1}\right)}=\frac{\mathrm{1}}{\mathrm{n}}−\frac{\mathrm{1}}{\mathrm{n}+\mathrm{1}}\Rightarrow\underset{\mathrm{n}=\mathrm{1}} {\overset{\infty} {\sum}}\frac{\mathrm{1}}{\mathrm{n}\left(\mathrm{n}+\mathrm{1}\right)}=\underset{\mathrm{n}=\mathrm{1}}…