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AllQuestion and Answers: Page 768

Question Number 143586    Answers: 1   Comments: 1

Question Number 141791    Answers: 4   Comments: 0

Calculate Σ_(n=1) ^(+∞) (n^2 /3^n )

$$\mathrm{Calculate} \\ $$$$\:\underset{\mathrm{n}=\mathrm{1}} {\overset{+\infty} {\sum}}\:\frac{\mathrm{n}^{\mathrm{2}} }{\mathrm{3}^{\mathrm{n}} } \\ $$

Question Number 141786    Answers: 1   Comments: 0

If y=1−cos2t and x=(√(1+t^2 )) .Show that (dy/dx)=((2(√(1+t^2 )) sin2t)/t) Help please.

$$\boldsymbol{\mathrm{If}}\:\:\boldsymbol{\mathrm{y}}=\mathrm{1}−\boldsymbol{\mathrm{cos}}\mathrm{2}\boldsymbol{\mathrm{t}}\:\:\boldsymbol{\mathrm{and}}\:\boldsymbol{\mathrm{x}}=\sqrt{\mathrm{1}+\boldsymbol{\mathrm{t}}^{\mathrm{2}} }\:.\boldsymbol{\mathrm{Show}}\:\boldsymbol{\mathrm{that}} \\ $$$$\frac{\boldsymbol{\mathrm{dy}}}{\boldsymbol{\mathrm{dx}}}=\frac{\mathrm{2}\sqrt{\mathrm{1}+\boldsymbol{\mathrm{t}}^{\mathrm{2}} }\:\boldsymbol{\mathrm{sin}}\mathrm{2}\boldsymbol{\mathrm{t}}}{\boldsymbol{\mathrm{t}}} \\ $$$$\boldsymbol{\mathrm{Help}}\:\boldsymbol{\mathrm{please}}. \\ $$

Question Number 141785    Answers: 1   Comments: 0

If x=asin2t+bcos2t,prove that (dx/dt)=2(√(a^2 +b^2 −x^2 )) Solution....

$$\boldsymbol{\mathrm{If}}\:\:\boldsymbol{\mathrm{x}}=\boldsymbol{\mathrm{asin}}\mathrm{2}\boldsymbol{\mathrm{t}}+\boldsymbol{\mathrm{bcos}}\mathrm{2}\boldsymbol{\mathrm{t}},\boldsymbol{\mathrm{prove}}\:\boldsymbol{\mathrm{that}}\: \\ $$$$\frac{\boldsymbol{\mathrm{dx}}}{\boldsymbol{\mathrm{dt}}}=\mathrm{2}\sqrt{\boldsymbol{\mathrm{a}}^{\mathrm{2}} +\boldsymbol{\mathrm{b}}^{\mathrm{2}} −\boldsymbol{\mathrm{x}}^{\mathrm{2}} } \\ $$$$\boldsymbol{\mathrm{Solution}}.... \\ $$

Question Number 141783    Answers: 0   Comments: 0

Question Number 141775    Answers: 1   Comments: 0

find ∫_0 ^∞ (e^(−x^2 ) /((x^2 +3)^2 ))dx

$$\mathrm{find}\:\int_{\mathrm{0}} ^{\infty} \:\frac{\mathrm{e}^{−\mathrm{x}^{\mathrm{2}} } }{\left(\mathrm{x}^{\mathrm{2}} \:+\mathrm{3}\right)^{\mathrm{2}} }\mathrm{dx} \\ $$

Question Number 141774    Answers: 2   Comments: 0

calculate ∫_0 ^∞ (e^(−x^2 ) /(1+x^2 ))dx

$$\mathrm{calculate}\:\int_{\mathrm{0}} ^{\infty} \:\:\frac{\mathrm{e}^{−\mathrm{x}^{\mathrm{2}} } }{\mathrm{1}+\mathrm{x}^{\mathrm{2}} }\mathrm{dx} \\ $$

Question Number 141769    Answers: 1   Comments: 0

If y=2sinx+tanx, prove that (d^2 y/dx^2 )=2sinx(sec^3 x−1) Any detailed solution please.

$$\boldsymbol{\mathrm{If}}\:\:\boldsymbol{\mathrm{y}}=\mathrm{2}\boldsymbol{\mathrm{sinx}}+\boldsymbol{\mathrm{tanx}},\:\boldsymbol{\mathrm{prove}}\:\boldsymbol{\mathrm{that}} \\ $$$$\frac{\boldsymbol{\mathrm{d}}^{\mathrm{2}} \boldsymbol{\mathrm{y}}}{\boldsymbol{\mathrm{dx}}^{\mathrm{2}} }=\mathrm{2}\boldsymbol{\mathrm{sinx}}\left(\boldsymbol{\mathrm{sec}}^{\mathrm{3}} \boldsymbol{\mathrm{x}}−\mathrm{1}\right) \\ $$$$\boldsymbol{\mathrm{Any}}\:\boldsymbol{\mathrm{detailed}}\:\boldsymbol{\mathrm{solution}}\:\boldsymbol{\mathrm{please}}. \\ $$

Question Number 141768    Answers: 0   Comments: 0

Let a,b,x,y > 0 and (a+x)(b+y) = (a+b)^2 . Prove that ((a−y)/x)+((b−x)/y) ≤ ((b−x)/a)+((a−y)/b)

$$\mathrm{Let}\:{a},{b},{x},{y}\:>\:\mathrm{0}\:\mathrm{and}\:\left({a}+{x}\right)\left({b}+{y}\right)\:=\:\left({a}+{b}\right)^{\mathrm{2}} \:.\:\:\:\:\:\:\:\: \\ $$$$\mathrm{Prove}\:\mathrm{that} \\ $$$$\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\frac{{a}−{y}}{{x}}+\frac{{b}−{x}}{{y}}\:\leqslant\:\frac{{b}−{x}}{{a}}+\frac{{a}−{y}}{{b}}\:\:\:\:\:\:\:\:\:\:\:\:\:\: \\ $$$$ \\ $$

Question Number 141759    Answers: 0   Comments: 0

Question Number 141757    Answers: 0   Comments: 1

Γ(n+(1/2))=(((√π)∙Γ(2n+1))/(2^(2n) Γ(n+1)))

$$\Gamma\left(\mathrm{n}+\frac{\mathrm{1}}{\mathrm{2}}\right)=\frac{\sqrt{\pi}\centerdot\Gamma\left(\mathrm{2n}+\mathrm{1}\right)}{\mathrm{2}^{\mathrm{2n}} \Gamma\left(\mathrm{n}+\mathrm{1}\right)} \\ $$

Question Number 141755    Answers: 0   Comments: 0

Question Number 141752    Answers: 1   Comments: 0

Question Number 141750    Answers: 1   Comments: 0

Question Number 141749    Answers: 1   Comments: 0

{ ((x^2 −y+(√(y^2 +5))=xy−(√(x−1)))),((y^2 +(√(xy+2))=2(x+y))) :} Find x,y

$$\begin{cases}{\mathrm{x}^{\mathrm{2}} −\mathrm{y}+\sqrt{\mathrm{y}^{\mathrm{2}} +\mathrm{5}}=\mathrm{xy}−\sqrt{\mathrm{x}−\mathrm{1}}}\\{\mathrm{y}^{\mathrm{2}} +\sqrt{\mathrm{xy}+\mathrm{2}}=\mathrm{2}\left(\mathrm{x}+\mathrm{y}\right)}\end{cases} \\ $$$$\mathrm{Find}\:\mathrm{x},\mathrm{y} \\ $$

Question Number 141777    Answers: 0   Comments: 1

A pack of 52 cards distributed equally to 4 people so as 4 cards each from same suit( of any 3 suit=4×3=12) and last card from 4th remaining suit . Number of such distributions is?

$${A}\:{pack}\:{of}\:\mathrm{52}\:{cards}\:{distributed}\:{equally}\:{to} \\ $$$$\mathrm{4}\:{people}\:{so}\:{as}\:\mathrm{4}\:{cards}\:{each}\:{from}\: \\ $$$${same}\:{suit}\left(\:{of}\:{any}\:\mathrm{3}\:{suit}=\mathrm{4}×\mathrm{3}=\mathrm{12}\right) \\ $$$${and}\:{last}\:{card}\:{from}\:\mathrm{4}{th}\:{remaining} \\ $$$${suit}\:.\:{Number}\:{of}\:{such} \\ $$$${distributions}\:{is}? \\ $$$$ \\ $$$$ \\ $$

Question Number 141733    Answers: 0   Comments: 0

Question Number 141730    Answers: 0   Comments: 2

x^2 +y^2 +xy=9 y^2 +z^2 +yz=16 x^2 +z^2 +xz=25 xy+yz+xz=?

$${x}^{\mathrm{2}} +{y}^{\mathrm{2}} +{xy}=\mathrm{9} \\ $$$${y}^{\mathrm{2}} +{z}^{\mathrm{2}} +{yz}=\mathrm{16} \\ $$$${x}^{\mathrm{2}} +{z}^{\mathrm{2}} +{xz}=\mathrm{25} \\ $$$${xy}+{yz}+{xz}=? \\ $$

Question Number 141753    Answers: 2   Comments: 1

∫(dx/(sinx+cosx))

$$\int\frac{{dx}}{{sinx}+{cosx}} \\ $$

Question Number 141781    Answers: 0   Comments: 2

help me to find the roots of x^5 +5x^4 +20x^3 +60x^2 +120x+120=0?

$${help}\:{me}\:{to}\:{find}\:{the}\:{roots}\:{of}\: \\ $$$${x}^{\mathrm{5}} +\mathrm{5}{x}^{\mathrm{4}} +\mathrm{20}{x}^{\mathrm{3}} +\mathrm{60}{x}^{\mathrm{2}} +\mathrm{120}{x}+\mathrm{120}=\mathrm{0}? \\ $$

Question Number 141794    Answers: 2   Comments: 2

Question Number 141779    Answers: 4   Comments: 0

lim_(x→0) (x^2 /(x+2−2(√(1+x)))) =?

$$\:\underset{{x}\rightarrow\mathrm{0}} {\mathrm{lim}}\:\:\frac{{x}^{\mathrm{2}} }{{x}+\mathrm{2}−\mathrm{2}\sqrt{\mathrm{1}+{x}}}\:=? \\ $$

Question Number 141747    Answers: 0   Comments: 0

Question Number 141776    Answers: 1   Comments: 0

The volume of a sphere is increasing at the constant rate of 10cm^3 /sec. Calculate the rate of increase of the surface area at the instant when the radius is 5cm.What is the radius of the sphere when the surface area is increasing at 2cm^2 /sec. Any step by step solution pls.

$$\boldsymbol{\mathrm{The}}\:\boldsymbol{\mathrm{volume}}\:\boldsymbol{\mathrm{of}}\:\boldsymbol{\mathrm{a}}\:\boldsymbol{\mathrm{sphere}}\:\boldsymbol{\mathrm{is}}\:\boldsymbol{\mathrm{increasing}} \\ $$$$\boldsymbol{\mathrm{at}}\:\boldsymbol{\mathrm{the}}\:\boldsymbol{\mathrm{constant}}\:\boldsymbol{\mathrm{rate}}\:\boldsymbol{\mathrm{of}}\:\mathrm{10}\boldsymbol{\mathrm{cm}}^{\mathrm{3}} /\boldsymbol{\mathrm{sec}}. \\ $$$$\boldsymbol{\mathrm{Calculate}}\:\boldsymbol{\mathrm{the}}\:\boldsymbol{\mathrm{rate}}\:\boldsymbol{\mathrm{of}}\:\boldsymbol{\mathrm{increase}}\:\boldsymbol{\mathrm{of}}\:\boldsymbol{\mathrm{the}}\: \\ $$$$\boldsymbol{\mathrm{surface}}\:\boldsymbol{\mathrm{area}}\:\boldsymbol{\mathrm{at}}\:\boldsymbol{\mathrm{the}}\:\boldsymbol{\mathrm{instant}}\:\boldsymbol{\mathrm{when}}\:\boldsymbol{\mathrm{the}} \\ $$$$\boldsymbol{\mathrm{radius}}\:\boldsymbol{\mathrm{is}}\:\mathrm{5}\boldsymbol{\mathrm{cm}}.\boldsymbol{\mathrm{What}}\:\boldsymbol{\mathrm{is}}\:\boldsymbol{\mathrm{the}}\:\boldsymbol{\mathrm{radius}}\:\boldsymbol{\mathrm{of}}\:\boldsymbol{\mathrm{the}} \\ $$$$\boldsymbol{\mathrm{sphere}}\:\boldsymbol{\mathrm{when}}\:\boldsymbol{\mathrm{the}}\:\boldsymbol{\mathrm{surface}}\:\boldsymbol{\mathrm{area}}\:\boldsymbol{\mathrm{is}}\:\boldsymbol{\mathrm{increasing}} \\ $$$$\boldsymbol{\mathrm{at}}\:\mathrm{2}\boldsymbol{\mathrm{cm}}^{\mathrm{2}} /\boldsymbol{\mathrm{sec}}. \\ $$$$\boldsymbol{\mathrm{Any}}\:\boldsymbol{\mathrm{step}}\:\boldsymbol{\mathrm{by}}\:\boldsymbol{\mathrm{step}}\:\boldsymbol{\mathrm{solution}}\:\boldsymbol{\mathrm{pls}}. \\ $$

Question Number 141719    Answers: 2   Comments: 0

∫_0 ^∞ (e^(−x^2 ) /((x^2 +(1/2))^2 ))dx=?

$$\int_{\mathrm{0}} ^{\infty} \frac{{e}^{−{x}^{\mathrm{2}} } }{\left({x}^{\mathrm{2}} +\frac{\mathrm{1}}{\mathrm{2}}\right)^{\mathrm{2}} }{dx}=? \\ $$

Question Number 141716    Answers: 1   Comments: 0

(x^2 lnx)y′′−xy′+y=0

$$\left({x}^{\mathrm{2}} {lnx}\right){y}''−{xy}'+{y}=\mathrm{0} \\ $$

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