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Question Number 120780 by mathace last updated on 02/Nov/20

solve x^2^x  =−(1/2)

solvex2x=12

Commented by Anuragkar last updated on 02/Nov/20

Use  Lambert W function to work it out......

UseLambertWfunctiontoworkitout......

Commented by Dwaipayan Shikari last updated on 02/Nov/20

Complex solution (x∈C).No real solution

Complexsolution(xC).Norealsolution

Answered by Anuragkar last updated on 14/Nov/20

2^x ln(x)=ln(e^(iπ) )−ln(2)  xln(x)ln(2)=ln(iπ−ln(2))  ln(x)e^(ln(x)) =ln(iπ−ln(2))/ln(2)  Now use lambert W function  W(ln(x)e^(ln(x)) )=ln(x)=W[ln{iπ−ln(2)}/ln(2)]      x=e^(W[ln{iπ−ln(2)}/ln(2)])     .....this is the final answer....calculstw it using   Wolframalpha

2xln(x)=ln(eiπ)ln(2)xln(x)ln(2)=ln(iπln(2))ln(x)eln(x)=ln(iπln(2))/ln(2)NowuselambertWfunctionW(ln(x)eln(x))=ln(x)=W[ln{iπln(2)}/ln(2)]x=eW[ln{iπln(2)}/ln(2)].....thisisthefinalanswer....calculstwitusingWolframalpha

Commented by Dwaipayan Shikari last updated on 13/Nov/20

Error in second line

Errorinsecondline

Answered by mathace last updated on 18/Nov/20

  x^2^x  =−(1/2)  2^x ln(x)=ln(e^(iπ) )−ln(2)  e^(xln (2)) ln(x)=iπ−ln(2)  ln(e^(xln (2)) ln (x))=ln (iπ−ln (2))  xln (2)+ln (ln (x))=ln (iπ−ln (2))  e^e^t  α+t=β where α=ln (2), β=ln (iπ−ln (2))  α+te^(−e^t ) =βe^(−e^t )   (t−β)e^(−e^t ) =−α  (t−β)e^(−(1+t+O(t^2 )) ) = −α  (t−β)e^(−(1+t) ) = −α  (t−β)e^(−t) =((−α)/e^(−1) )=−αe  (β−t)e^(−t) =αe  (β−t)e^(−t) e^β =αe^(β+1)   (β−t)e^(β−t) =αe^(β+1)   W((β−t)e^(β−t) )=W(αe^(β+1) )  β−t=W(αe^(β+1) )  t=β−W(αe^(β+1) )  Now recalling  x=e^e^t    x=e^e^(β−W(αe^(β+1) ))    Recalling the value of α and β, we get  the required solution.  (Omar)

x2x=122xln(x)=ln(eiπ)ln(2)exln(2)ln(x)=iπln(2)ln(exln(2)ln(x))=ln(iπln(2))xln(2)+ln(ln(x))=ln(iπln(2))eetα+t=βwhereα=ln(2),β=ln(iπln(2))α+teet=βeet(tβ)eet=α(tβ)e(1+t+O(t2))=α(tβ)e(1+t)=α(tβ)et=αe1=αe(βt)et=αe(βt)eteβ=αeβ+1(βt)eβt=αeβ+1W((βt)eβt)=W(αeβ+1)βt=W(αeβ+1)t=βW(αeβ+1)Nowrecallingx=eetx=eeβW(αeβ+1)Recallingthevalueofαandβ,wegettherequiredsolution.(Omar)

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