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 #4
avatar+223 
+2
Feb 13, 2018
 #2
avatar+26396 
+1

Solve and find the domain of the equation:

xlogx(x2)=9

 

1. Domain:

x2>0x>2

 {xR:x>2} (assuming a function from reals to reals) 

 

2. Solve:

xlogx(x2)=9logx(x2)=ln(x2)ln(x)=ln(x2)ln(x12)=ln(x2)12ln(x)=2ln(x2)ln(x)x2ln(x2)ln(x)=9Formula: ab=eln(ab)=ebln(a)x2ln(x2)ln(x)=e2ln(x2)ln(x)ln(x)=e2ln(x2)

 

e2ln(x2)=9eln((x2)2)=9|eln((x2)2)=(x2)2(x2)2=9| both sidesx2=±3x12=3x1=3+2x1=5x22=3x2=3+2x2=1|no solution, see domain x>2

 

laugh

Feb 13, 2018

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