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Question Number 73036 Answers: 1 Comments: 3
$$\left.{calculate}\:\mathrm{1}\right)\:\sum_{{k}=\mathrm{1}} ^{{n}} \:{k}^{\mathrm{2}} \left({n}+\mathrm{1}−{k}\right) \\ $$$$\left.\mathrm{2}\right)\sum_{\mathrm{1}\leqslant{i}\leqslant{j}\leqslant{n}} \:{ij} \\ $$
Question Number 73035 Answers: 0 Comments: 0
$${prove}\:{that}\:\:\forall{n}\in{N}^{\bigstar} \:\:\:\:\:\mathrm{2}!\mathrm{4}!....\left(\mathrm{2}{n}\right)!\geqslant\left\{\left({n}+\mathrm{1}\right)!\right\}^{{n}} \\ $$
Question Number 73034 Answers: 1 Comments: 1
$${calculate}\:{U}_{{n}} =\sum_{{k}=\mathrm{1}} ^{{n}} \:\frac{{k}}{\left({k}+\mathrm{1}\right)!} \\ $$
Question Number 73033 Answers: 1 Comments: 0
$${solve}\:{inside}\:{N}^{\mathrm{2}} \:\:\:\:{x}\left({x}+\mathrm{1}\right)=\mathrm{4}{y}\left({y}+\mathrm{1}\right) \\ $$
Question Number 73032 Answers: 1 Comments: 0
$${find}\:{x}\:{from}\:{n}\:\:/\:\exists{n}\in{N}^{{n}} \:\:\:\:{and}\:\mathrm{1}+{x}+{x}^{\mathrm{2}} \:+{x}^{\mathrm{3}} \:+{x}^{\mathrm{4}} ={n}^{\mathrm{2}} \\ $$
Question Number 73031 Answers: 0 Comments: 0
$${solve}\:{inside}\:{N}^{\mathrm{2}} \:\:\:\mathrm{3}{x}^{\mathrm{3}} \:+{xy}\:+\mathrm{4}{y}^{\mathrm{3}} \:=\mathrm{349} \\ $$
Question Number 73030 Answers: 2 Comments: 0
Question Number 73029 Answers: 1 Comments: 0
$${prove}\:{that}\:\:\forall\left({n},{p},{q}\right)\in{N}^{\mathrm{3}} \:\:\sum_{{k}=\mathrm{0}} ^{{n}} \:{C}_{{p}} ^{{k}} \:{C}_{{q}} ^{{n}−{k}} \:\:\:={C}_{{p}+{q}} ^{{n}} \\ $$$${conclude}\:{that}\:\sum_{{k}=\mathrm{0}} ^{{n}} \:\left({C}_{{n}} ^{{k}} \right)^{\mathrm{2}} \:={C}_{\mathrm{2}{n}} ^{{n}} \\ $$
Question Number 73028 Answers: 2 Comments: 0
$${calculate}\:\sum_{\mathrm{1}\leqslant{i}\leqslant{n}\:{and}\:\mathrm{1}\leqslant{j}\leqslant{n}} \:\:{min}\left({i},{j}\right) \\ $$
Question Number 73027 Answers: 1 Comments: 0
$${x}\:{and}\:{y}\:{are}\:{reals}\left({or}\:{complex}\right)\:{let}\:{put}\:{x}^{\left(\mathrm{0}\right)} =\mathrm{1}\:,{x}^{\left(\mathrm{1}\right)} ={x} \\ $$$${x}^{\left(\mathrm{2}\right)} ={x}\left({x}−\mathrm{1}\right).....{x}^{\left({n}\right)} ={x}\left({x}−\mathrm{1}\right)\left({x}−\mathrm{2}\right)...\left({x}−{n}+\mathrm{1}\right){prove}\:{that} \\ $$$$\left({x}+{y}\right)^{\left({n}\right)} =\sum_{{k}=\mathrm{0}} ^{{n}} \:{C}_{{n}} ^{{k}} \:\:{x}^{\left({n}−{k}\right)} {y}^{\left({k}\right)} \\ $$
Question Number 73021 Answers: 0 Comments: 0
Question Number 73017 Answers: 0 Comments: 1
$${find}\: \\ $$$$\:\underset{{x}\rightarrow+\infty} {\mathrm{lim}}\:\:{x}\sqrt{{x}^{\mathrm{2}} \:+\:\mathrm{1}}\: \\ $$
Question Number 73084 Answers: 1 Comments: 0
Question Number 72998 Answers: 0 Comments: 0
$${The}\:{acute}\:{angle}\:{of}\:{the}\:{rectangle}\:{trapezius}\:{is}\:{equal}\:{to}\:\alpha=\mathrm{90}°{arcsin}\mathrm{0}.\mathrm{1} \\ $$$${The}\:{bases}\:{measure}\:\mathrm{10}\:{and}\:\mathrm{30}.\:{Calculate}\:{the}\:{area}\:{of}\:{the}\:{trapezius}. \\ $$
Question Number 72997 Answers: 1 Comments: 0
$${The}\:{area}\:{of}\:{the}\:{equilateral}\:{triangle}\:{is}\:{equal}\:{to}\:\frac{\sqrt{\mathrm{16}}\sqrt{\mathrm{8}}}{\mathrm{3}\sqrt{\pi}} \\ $$$${Calculate}\:{the}\:{area}\:{of}\:{the}\:{circle}\:{inscribed}\:{in}\:{the}\:{triangle}. \\ $$$$\: \\ $$
Question Number 72990 Answers: 1 Comments: 1
$${calculate}\:{lim}_{{x}\rightarrow\mathrm{0}} \:\:\:\:\:\frac{{arctan}\left({e}^{{x}} \right)−\frac{\pi}{\mathrm{4}}}{{x}^{\mathrm{2}} } \\ $$
Question Number 72988 Answers: 1 Comments: 1
$${calculate}\:{f}\left({x}\right)=\int_{\mathrm{0}} ^{\infty} \:\:\:\:\frac{{e}^{−{xt}^{\mathrm{2}} } }{\mathrm{4}+{t}^{\mathrm{2}} }{dt}\:\:\:{with}\:{x}>\mathrm{0} \\ $$
Question Number 72986 Answers: 0 Comments: 0
$${calculate}\:\:\int_{\mathrm{0}} ^{\infty} \:\:\frac{{e}^{−{x}^{\mathrm{2}} } \:\:{cosx}}{\left({x}^{\mathrm{2}} +{x}+\mathrm{1}\right)^{\mathrm{2}} }{dx} \\ $$
Question Number 72965 Answers: 1 Comments: 1
$$\mathrm{Prove}\:\mathrm{that}\:\mathrm{this}\:\mathrm{equation}\:\mathrm{is}\:\mathrm{true}: \\ $$$$\underset{{x}=\mathrm{1}} {\overset{{n}−\mathrm{1}} {\prod}}\left(\mathrm{2}{x}+\mathrm{1}\right)=\frac{\left(\mathrm{2}{x}−\mathrm{1}\right)!}{\left(\mathrm{2}\right)^{{x}−\mathrm{1}} \left({x}−\mathrm{1}\right)!} \\ $$
Question Number 72952 Answers: 2 Comments: 4
Question Number 72931 Answers: 2 Comments: 0
$${Find}\:{the}\:{numeric}\:{value}\:{of} \\ $$$$\frac{\mathrm{2}−\mathrm{sin}\:^{\mathrm{2}} \left(\alpha\right)}{\mathrm{cos}\:^{\mathrm{2}} \left(\alpha\right)−\mathrm{tan}\:^{\mathrm{2}} \left(\alpha\right)} \\ $$
Question Number 72930 Answers: 1 Comments: 0
Question Number 73012 Answers: 4 Comments: 0
$$\int\sqrt{{tan}\mathrm{x}}\:{d}\mathrm{x} \\ $$
Question Number 72912 Answers: 1 Comments: 0
$${calculate}\:{S}_{{p}} =\:\sum_{{n}=\mathrm{0}} ^{\infty} \:\frac{\left(−\mathrm{1}\right)^{{n}} }{{n}+{p}} \\ $$
Question Number 72908 Answers: 2 Comments: 15
$${find}\:\int_{\mathrm{0}} ^{\pi} \:\:\frac{{d}\theta}{{x}^{\mathrm{2}} −\mathrm{2}{x}\:{cos}\theta\:+\mathrm{1}}\:\:{with}\:{x}\:{real}. \\ $$
Question Number 72900 Answers: 1 Comments: 0
$${prove}\:{that}\: \\ $$$$ \\ $$$$−\mid{a}\mid\leqslant{a}\leqslant\mid{a}\mid \\ $$$$ \\ $$$${a}\:{is}\:{a}\:{real}\:{number} \\ $$
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