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Question Number 42020    Answers: 0   Comments: 0

let S_n (x)=Σ_(k=1) ^n (x^k /(√k)) find a equivalent of S_n (x) when n→+∞

$${let}\:\:{S}_{{n}} \left({x}\right)=\sum_{{k}=\mathrm{1}} ^{{n}} \:\frac{{x}^{{k}} }{\sqrt{{k}}} \\ $$$${find}\:{a}\:{equivalent}\:{of}\:{S}_{{n}} \left({x}\right)\:{when}\:{n}\rightarrow+\infty \\ $$

Question Number 42019    Answers: 1   Comments: 3

find x: 2^x + 3^x = 13

$$\mathrm{find}\:\mathrm{x}:\:\:\:\:\:\mathrm{2}^{\mathrm{x}} \:+\:\mathrm{3}^{\mathrm{x}} \:=\:\mathrm{13} \\ $$

Question Number 42012    Answers: 2   Comments: 0

Solve : (du/dt) = ((3u−7t)/(−7u+3t))

$$\mathrm{Solve}\:: \\ $$$$\frac{{d}\mathrm{u}}{{d}\mathrm{t}}\:=\:\frac{\mathrm{3u}−\mathrm{7t}}{−\mathrm{7u}+\mathrm{3t}} \\ $$

Question Number 42009    Answers: 1   Comments: 0

if (a+bω+cω^2 )+(aω+bω^2 +c)^2 +(aω^2 +b+cω)^2 =0 then prove that a=c or a+c=2b

$$\mathrm{if}\:\left(\mathrm{a}+\mathrm{b}\omega+\mathrm{c}\omega^{\mathrm{2}} \right)+\left(\mathrm{a}\omega+\mathrm{b}\omega^{\mathrm{2}} +\mathrm{c}\right)^{\mathrm{2}} +\left(\mathrm{a}\omega^{\mathrm{2}} +\mathrm{b}+\mathrm{c}\omega\right)^{\mathrm{2}} =\mathrm{0} \\ $$$$\mathrm{then}\:\mathrm{prove}\:\mathrm{that}\:\mathrm{a}=\mathrm{c}\:\:\mathrm{or}\:\:\:\mathrm{a}+\mathrm{c}=\mathrm{2b} \\ $$

Question Number 42007    Answers: 2   Comments: 0

Question Number 41998    Answers: 1   Comments: 0

lim_(x→∞) ((x + cos x)/(x + sin x))

$$\underset{{x}\rightarrow\infty} {\mathrm{lim}}\:\frac{{x}\:+\:\mathrm{cos}\:{x}}{{x}\:+\:\mathrm{sin}\:{x}} \\ $$

Question Number 41989    Answers: 2   Comments: 1

Question Number 41985    Answers: 1   Comments: 1

Prove e^x ≥x+1 ∀x∈R in as many ways as you can show

$$\mathrm{Prove}\:{e}^{{x}} \geqslant{x}+\mathrm{1}\:\forall{x}\in\mathbb{R}\:\mathrm{in}\:\mathrm{as}\:\mathrm{many}\:\mathrm{ways} \\ $$$$\mathrm{as}\:\mathrm{you}\:\mathrm{can}\:\mathrm{show} \\ $$

Question Number 41984    Answers: 2   Comments: 7

solve simultaneously: 2(√k) + h = 9 ....... (i) k + 2(√h) = 3 ....... (ii)

$$\mathrm{solve}\:\mathrm{simultaneously}:\:\:\:\:\:\:\:\:\:\:\:\mathrm{2}\sqrt{\mathrm{k}}\:\:+\:\mathrm{h}\:=\:\mathrm{9}\:\:\:.......\:\left(\mathrm{i}\right) \\ $$$$\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\mathrm{k}\:+\:\mathrm{2}\sqrt{\mathrm{h}}\:\:=\:\mathrm{3}\:\:.......\:\left(\mathrm{ii}\right) \\ $$

Question Number 41966    Answers: 1   Comments: 0

Question Number 41964    Answers: 1   Comments: 10

Prof Kintush has a near point of 45cm and his far point is infinity. What type of lens and focal length should be recommended for his normal reading?

$${Prof}\:{Kintush}\:{has}\:{a}\:{near}\:{point}\:{of} \\ $$$$\mathrm{45}{cm}\:{and}\:{his}\:{far}\:{point}\:{is}\:{infinity}. \\ $$$${What}\:{type}\:{of}\:{lens}\:{and}\:{focal}\:{length} \\ $$$${should}\:{be}\:{recommended}\:{for}\:{his} \\ $$$${normal}\:{reading}? \\ $$

Question Number 41958    Answers: 1   Comments: 0

{ ((x^(√y) +y^(√x) =((49)/(48)))),(((√x)+(√y)=(7/2))) :} find x and y k.k

$$\begin{cases}{\mathrm{x}^{\sqrt{\mathrm{y}}} +\mathrm{y}^{\sqrt{\mathrm{x}}} =\frac{\mathrm{49}}{\mathrm{48}}}\\{\sqrt{\mathrm{x}}+\sqrt{\mathrm{y}}=\frac{\mathrm{7}}{\mathrm{2}}}\end{cases} \\ $$$$\mathrm{find}\:\mathrm{x}\:\mathrm{and}\:\mathrm{y} \\ $$$$\mathrm{k}.\mathrm{k} \\ $$

Question Number 41957    Answers: 1   Comments: 1

Question Number 41913    Answers: 1   Comments: 0

let f(a) = ∫_0 ^π (x/(1+acosx))dx 1) find f(a) 2) calculate ∫_0 ^π (x/(1+2cosx))dx and ∫_0 ^π (x/(1−2cosx))dx 3) calculate ∫_0 ^π ((xcosx)/((1+acosx)^2 ))dx 4) find the value of ∫_0 ^π ((xcosx)/((1+2cosx)^2 ))dx .

$${let}\:{f}\left({a}\right)\:=\:\int_{\mathrm{0}} ^{\pi} \:\:\:\:\frac{{x}}{\mathrm{1}+{acosx}}{dx} \\ $$$$\left.\mathrm{1}\right)\:{find}\:\:{f}\left({a}\right)\: \\ $$$$\left.\mathrm{2}\right)\:{calculate}\:\:\int_{\mathrm{0}} ^{\pi} \:\:\:\frac{{x}}{\mathrm{1}+\mathrm{2}{cosx}}{dx}\:{and}\:\int_{\mathrm{0}} ^{\pi} \:\:\:\frac{{x}}{\mathrm{1}−\mathrm{2}{cosx}}{dx} \\ $$$$\left.\mathrm{3}\right)\:{calculate}\:\:\int_{\mathrm{0}} ^{\pi} \:\:\frac{{xcosx}}{\left(\mathrm{1}+{acosx}\right)^{\mathrm{2}} }{dx} \\ $$$$\left.\mathrm{4}\right)\:{find}\:{the}\:{value}\:{of}\:\:\int_{\mathrm{0}} ^{\pi} \:\:\:\frac{{xcosx}}{\left(\mathrm{1}+\mathrm{2}{cosx}\right)^{\mathrm{2}} }{dx}\:. \\ $$

Question Number 41912    Answers: 2   Comments: 0

The estimated time for Abu and Ali to repair a faulty car is six hours. If Abu used 10 hours to repair the car, how many hours will Ali use to repair the car?

$$\mathrm{The}\:\mathrm{estimated}\:\mathrm{time}\:\mathrm{for}\:\mathrm{Abu}\:\mathrm{and}\:\mathrm{Ali}\:\mathrm{to}\:\mathrm{repair}\:\mathrm{a} \\ $$$$\mathrm{faulty}\:\mathrm{car}\:\mathrm{is}\:\mathrm{six}\:\mathrm{hours}.\:\mathrm{If}\:\mathrm{Abu}\:\mathrm{used}\:\mathrm{10}\:\mathrm{hours}\:\mathrm{to} \\ $$$$\mathrm{repair}\:\mathrm{the}\:\mathrm{car},\:\mathrm{how}\:\mathrm{many}\:\mathrm{hours}\:\mathrm{will}\:\mathrm{Ali}\:\mathrm{use}\:\mathrm{to}\:\mathrm{repair} \\ $$$$\mathrm{the}\:\mathrm{car}? \\ $$

Question Number 41911    Answers: 2   Comments: 5

h(x)=(√(sin^4 x+cos^4 x−2msinxcosx)) Find all the values of the parameter m for the funtion denined on R

$${h}\left({x}\right)=\sqrt{{sin}^{\mathrm{4}} {x}+{cos}^{\mathrm{4}} {x}−\mathrm{2}{msinxcosx}} \\ $$$${Find}\:{all}\:{the}\:{values}\:{of}\:{the}\:{parameter}\:{m}\:{for}\:{the}\:{funtion}\:{denined}\:{on}\:{R} \\ $$$$ \\ $$

Question Number 41906    Answers: 0   Comments: 1

A concave lens of focal length 60cm is made of material whose refractive index for red light is 1.641 and refractive index for blue light is 1.659.That for white light is 1.65.It is combined with a convex lens of dispersive power 0.0173 to form an achromatic doublet. Calculate the focal length of the achromatic lens.

$${A}\:{concave}\:{lens}\:{of}\:{focal}\:{length}\:\mathrm{60}{cm} \\ $$$${is}\:{made}\:{of}\:{material}\:{whose} \\ $$$${refractive}\:{index}\:{for}\:{red}\:{light}\:{is} \\ $$$$\mathrm{1}.\mathrm{641}\:{and}\:{refractive}\:{index}\:{for}\:{blue} \\ $$$${light}\:{is}\:\mathrm{1}.\mathrm{659}.{That}\:{for}\:{white}\:{light} \\ $$$${is}\:\mathrm{1}.\mathrm{65}.{It}\:{is}\:{combined}\:{with}\:{a}\:{convex} \\ $$$${lens}\:{of}\:{dispersive}\:{power}\:\mathrm{0}.\mathrm{0173}\:{to} \\ $$$${form}\:{an}\:{achromatic}\:{doublet}. \\ $$$${Calculate}\:{the}\:{focal}\:{length}\:{of}\:{the} \\ $$$${achromatic}\:{lens}. \\ $$

Question Number 41962    Answers: 1   Comments: 1

A student holding a 324Hz tuning fork approaches a wall at a speed of 6ms^(−1) .The speed of sound in air is 336ms^(−1) .What frequency will the student detect from waves omitted from the fork and waves coming from the wall?

$${A}\:{student}\:{holding}\:{a}\:\mathrm{324}{Hz}\:{tuning} \\ $$$${fork}\:{approaches}\:{a}\:{wall}\:{at}\:{a}\:{speed} \\ $$$${of}\:\mathrm{6}{ms}^{−\mathrm{1}} .{The}\:{speed}\:{of}\:{sound}\:{in}\:{air} \\ $$$${is}\:\mathrm{336}{ms}^{−\mathrm{1}} .{What}\:{frequency}\:{will} \\ $$$${the}\:{student}\:{detect}\:{from}\:{waves} \\ $$$${omitted}\:{from}\:{the}\:{fork}\:{and}\:{waves} \\ $$$${coming}\:{from}\:{the}\:{wall}? \\ $$

Question Number 41902    Answers: 1   Comments: 0

tan3θ tan2θ =1 find the general^(solution......)

$$\mathrm{tan3}\theta\:\mathrm{tan2}\theta\:=\mathrm{1} \\ $$$$\mathrm{find}\:\mathrm{the}\:\mathrm{general}\:^{\mathrm{solution}......} \\ $$

Question Number 41921    Answers: 2   Comments: 0

Find x : 625^(x − 5) = 200((√x))^3

$$\mathrm{Find}\:\mathrm{x}\::\:\:\:\:\:\:\:\:\:\:\:\:\mathrm{625}^{\mathrm{x}\:−\:\mathrm{5}} \:=\:\mathrm{200}\left(\sqrt{\mathrm{x}}\right)^{\mathrm{3}} \\ $$

Question Number 41896    Answers: 2   Comments: 1

∫_(−1/2) ^(1/2) [ (((x+1)/(x−1)))^2 +(((x−1)/(x+1)))^2 −2]^(1/2) dx =

$$\underset{−\mathrm{1}/\mathrm{2}} {\overset{\mathrm{1}/\mathrm{2}} {\int}}\:\:\left[\:\left(\frac{{x}+\mathrm{1}}{{x}−\mathrm{1}}\right)^{\mathrm{2}} +\left(\frac{{x}−\mathrm{1}}{{x}+\mathrm{1}}\right)^{\mathrm{2}} −\mathrm{2}\right]^{\mathrm{1}/\mathrm{2}} {dx}\:= \\ $$

Question Number 41895    Answers: 1   Comments: 1

(√3)sin3x−cos3x+2sin((9x)/4)=4

$$\sqrt{\mathrm{3}}{sin}\mathrm{3}{x}−{cos}\mathrm{3}{x}+\mathrm{2}{sin}\frac{\mathrm{9}{x}}{\mathrm{4}}=\mathrm{4} \\ $$

Question Number 41888    Answers: 0   Comments: 5

The length of mercury column in a mercury-in-glass thermometer is 4cm at triple point.What is the length of the column when the scale indicates temperature of 560K.

$${The}\:{length}\:{of}\:{mercury}\:{column}\:{in} \\ $$$${a}\:{mercury}-{in}-{glass}\:{thermometer} \\ $$$${is}\:\mathrm{4}{cm}\:{at}\:{triple}\:{point}.{What}\:{is}\:{the} \\ $$$${length}\:{of}\:{the}\:{column}\:{when}\:{the} \\ $$$${scale}\:{indicates}\:{temperature}\:{of} \\ $$$$\mathrm{560}{K}. \\ $$

Question Number 41887    Answers: 1   Comments: 0

x+(√y)+xy=82 (√x)+y+(√(xy))=16 Find x and y by khaled.k

$$\mathrm{x}+\sqrt{\mathrm{y}}+\mathrm{xy}=\mathrm{82} \\ $$$$\sqrt{\mathrm{x}}+\mathrm{y}+\sqrt{\mathrm{xy}}=\mathrm{16} \\ $$$$\mathrm{Find}\:\mathrm{x}\:\mathrm{and}\:\mathrm{y} \\ $$$$\mathrm{by}\:\mathrm{khaled}.\mathrm{k} \\ $$

Question Number 41879    Answers: 1   Comments: 0

If a fraction is added to its denominator , it reduces to (1/2) and when the same fraction added to numerator, it also reduces to (2/3) (a) what is the fraction (b) find the square root such that the result of the fraction is less than 1

$$\mathrm{If}\:\mathrm{a}\:\mathrm{fraction}\:\mathrm{is}\:\mathrm{added}\:\mathrm{to}\:\mathrm{its}\:\mathrm{denominator}\:,\:\:\mathrm{it}\:\mathrm{reduces}\:\mathrm{to}\:\frac{\mathrm{1}}{\mathrm{2}}\:\mathrm{and}\: \\ $$$$\mathrm{when}\:\mathrm{the}\:\mathrm{same}\:\mathrm{fraction}\:\mathrm{added}\:\mathrm{to}\:\mathrm{numerator},\:\mathrm{it}\:\mathrm{also}\:\mathrm{reduces}\:\mathrm{to}\:\frac{\mathrm{2}}{\mathrm{3}} \\ $$$$\left(\mathrm{a}\right)\:\mathrm{what}\:\mathrm{is}\:\mathrm{the}\:\mathrm{fraction} \\ $$$$\left(\mathrm{b}\right)\:\mathrm{find}\:\mathrm{the}\:\mathrm{square}\:\mathrm{root}\:\mathrm{such}\:\mathrm{that}\:\mathrm{the}\:\mathrm{result}\:\mathrm{of}\:\mathrm{the}\:\mathrm{fraction}\:\mathrm{is}\:\mathrm{less} \\ $$$$\mathrm{than}\:\mathrm{1} \\ $$$$ \\ $$

Question Number 41878    Answers: 1   Comments: 0

(√3)sin3x−cos3x+2sin((9x)/4)=2

$$\sqrt{\mathrm{3}}{sin}\mathrm{3}{x}−{cos}\mathrm{3}{x}+\mathrm{2}{sin}\frac{\mathrm{9}{x}}{\mathrm{4}}=\mathrm{2} \\ $$

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