+0  
 
0
40
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avatar+748 

Hi good people!!!....

 

The sum is:

\(x-3 \sqrt{x+2}=2\)

 

when we solve x, we get x=14 or x=-1

-1 is rendered na, but 14, not---why is this?

If I replace x with -1, we get

 \(-1-3 \sqrt{-1+2}=2\)

which is \(-4 \sqrt{1}=2\)

which is \(-4=2\)...which of course is NOT..

 

But the same goes for the 14??

\(14-3 \sqrt{14+2}=2\)

which is \(11 \sqrt{16}=2\)

which is \(44=2\)

 

which also is NOT???

 

all and any answer is very appreciated!..thank you all kindly.

 Oct 12, 2020
 #1
avatar+27695 
0

-1` - 3 sqrt(-1+2)    = 2  ?????    no it does not...it equals  -4

 

the solutions you obtained are both incorrect...you made a mistake somewhere (we ALL do !)

   ......go back and solve it again to get different answers

 
 Oct 12, 2020
 #2
avatar+27695 
+1

Update :     I looked at it a little closer:

 

x-2  = 3 (sqrt(x+2))   square both sides

x^2 - 4x + 4   = 9 (x+2)

x^2 -13x -14  = 0

 

Quadratic equation shows x = -1   and 14

 

14 - 3 sqrt (14+2) = 2

14 - 3 (sqrt16) = 2             ( look at your step where you get    11 sqrt (16)   <---- this is where you made your error)

14 - 12 = 2                           so 14 IS an answer     only -1 is NOT.

 
 Oct 12, 2020
edited by ElectricPavlov  Oct 12, 2020
edited by ElectricPavlov  Oct 12, 2020
 #3
avatar+748 
+1

aawww, you know what I did?????...I did not follow the order of operations when I checked the roots.....Thank you for your time, I do appreciate..

 
juriemagic  Oct 12, 2020
 #4
avatar+111124 
0

Hi Juriemagic,

It is really good to see you here.     laugh

 
 Oct 12, 2020

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