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f-x-0-x-t-x-dt-x-gt-1-lim-x-1-f-x-f-x-1-f-x-




Question Number 1594 by 123456 last updated on 24/Aug/15
f(x)=∫_0 ^x t^x dt,x>−1  lim_(x→−1^+ ) f(x)=?  f(x+1)−f(x)=?
f(x)=x0txdt,x>1limx1+f(x)=?f(x+1)f(x)=?
Commented by 112358 last updated on 25/Aug/15
f(x)=∫_0 ^x t^x dt=(t^(x+1) /(x+1))∣_0 ^x =(1/(x+1))(x^(x+1) −0^(x+1) )  f(x)=(1/(x+1))x^(x+1)  ,x>−1  f(x+1)−f(x)=(1/(x+2))(x+1)^(x+2) −(1/(x+1))x^(x+1)   rhs=(((x+1)^2 )/(x+2))(x+1)^x −(x/(x+1))x^x             =((x^2 +2x+1)/(x+2))(x+1)^x −(x/(x+1))x^x            =((x(x+2)+1)/(x+2))(x+1)^x −(x/(x+1))x^x            =x[(x+1)^x −(x^x /(x+1))]+(((x+1)^x )/(x+2))            =x[(((x+1)^(x+1) −x^x )/(x+1))]+(((x+1)^x )/(x+2))             =((x{(x+1)^(x+1) −x^x }(x+2)+(x+1)^(x+1) )/((x+1)(x+2)))              =((x^2 (x+1)^(x+1) +2x(x+1)^(x+1) +(x+1)^(x+1) −x^(x+2) −2x^(x+1) )/((x+1)(x+2)))  f(x+1)−f(x)=(((x+1)^(x+3) −x^(x+1) (x+2))/((x+1)(x+2)))  f(x)=(1/(1+x))x^(x+1) =(x/(1+x))x^x =(1−(1/(x+1)))x^x   Let L=lim_(x→−1^+ ) f(x) (if this limit exists)  L=lim_(x→−1^+ ) f(x)=lim_(x→−1^+ ) [(1−(1/(x+1)))x^x ]  L=[lim_(x→−1^+ ) (1−(1/(x+1)))]×[lim_(x→−1^+ ) x^x ]  Let p=lim_(x→−1^+ ) x^x   p=lim_(x→−1^+ ) x^x =lim_(x→−1^+ ) e^(lnx^x ) =lim_(x→−1^+ ) e^(xlnx)   p=e^(lim_(x→−1^+ ) xlnx) =e^((lim_(x→−1^+ ) x)(lim_(x→−1^+ ) lnx))   p=e^(−1×ln(−1)) =e^(ln(−1)) =e^(ln1+iπ)   p=e^(iπ) =−1  Let q=lim_(x→−1^+ ) (1−(1/(x+1)))  (1/(1+x))=(1+x)^(−1) ⇒ (1/(1+x))=e^(−ln(x+1))   ∴q=lim_(x→−1^+ ) 1−exp(−lim_(x→−1^+ ) ln(x+1))  Now, lim_(x→−1^+ ) ln(x+1)=−∞  ∴ q=1−exp(−1×−∞)=−∞  ∵ L=p×q⇒L=−∞×−1=∞  L does not exist.  ⇒lim_(x→−1^+ ) f(x) does not exist
f(x)=0xtxdt=tx+1x+10x=1x+1(xx+10x+1)f(x)=1x+1xx+1,x>1f(x+1)f(x)=1x+2(x+1)x+21x+1xx+1rhs=(x+1)2x+2(x+1)xxx+1xx=x2+2x+1x+2(x+1)xxx+1xx=x(x+2)+1x+2(x+1)xxx+1xx=x[(x+1)xxxx+1]+(x+1)xx+2=x[(x+1)x+1xxx+1]+(x+1)xx+2=x{(x+1)x+1xx}(x+2)+(x+1)x+1(x+1)(x+2)=x2(x+1)x+1+2x(x+1)x+1+(x+1)x+1xx+22xx+1(x+1)(x+2)f(x+1)f(x)=(x+1)x+3xx+1(x+2)(x+1)(x+2)f(x)=11+xxx+1=x1+xxx=(11x+1)xxLetL=limx1+f(x)(ifthislimitexists)L=limx1+f(x)=limx1+[(11x+1)xx]L=[limx1+(11x+1)]×[limx1+xx]Letp=limx1+xxp=limx1+xx=limx1+elnxx=limx1+exlnxp=elimx1+xlnx=e(limx1+x)(limx1+lnx)p=e1×ln(1)=eln(1)=eln1+iπp=eiπ=1Letq=limx1+(11x+1)11+x=(1+x)111+x=eln(x+1)q=lim1x1+exp(limx1+ln(x+1))Now,limx1+ln(x+1)=q=1exp(1×)=L=p×qL=×1=Ldoesnotexist.limx1+f(x)doesnotexist
Commented by Rasheed Soomro last updated on 24/Aug/15
Excelent!
Excelent!

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