SOLUTION: {{{sqrt(2x-3)+x=3}}}

Algebra ->  Real-numbers -> SOLUTION: {{{sqrt(2x-3)+x=3}}}      Log On


   



Question 146049: sqrt%282x-3%29%2Bx=3
Answer by Edwin McCravy(20054) About Me  (Show Source):
You can put this solution on YOUR website!

 sqrt%282x-3%29%2Bx=3

Isolate the radical by adding -x to both sides:

 sqrt%282x-3%29%2Bx-x=3-x

 sqrt%282x-3%29=3-x

Now square both sides:

 %28sqrt%282x-3%29%29%5E2=%283-x%29%5E2

On the left side, to square a square root takes 
away the radical and the exponent. We write the
right side as %283-x%29%283-x%29

 2x-3=%283-x%29%283-x%29

Use FOIL on the right side

2x-3=9-3x-3x%2Bx%5E2

2x-3=9-6x%2Bx%5E2

See if you can go from there to:

x%5E2-8x%2B12=0

Then we factor the left side:

%28x-6%29%28x-2%29=0

Use the zero factor principle,
and set each factor = 0:

x-6=0 gives x=6

x-2=0 gives x=2

But we must check both solutions in the
original equations, because in radical 
equations, there may be extraneous (bogus) 
solutions.

Checking x=6 in the original equation:

 sqrt%282x-3%29%2Bx=3
 sqrt%282%286%29-3%29%2B%286%29=3
 sqrt%2812-3%29%2B6=3
 sqrt%289%29%2B6=3
 3%2B6=3
 9=3

That is false, so x=6 is not a solution
to the original equation.

Checking x=2 in the original equation:

 sqrt%282x-3%29%2Bx=3
 sqrt%282%282%29-3%29%2B%282%29=3
 sqrt%284-3%29%2B2=3
 sqrt%281%29%2B2=3
 1%2B2=3
 3=3

That is true, so x=2 is the only solution
to the original equation.

---------------------

If you look at the graph of the left side of 

sqrt%282x-3%29%2Bx=3

that is, plot y=sqrt%282x-3%29%2Bx

you get this curve:



and if you plot the right side of

sqrt%282x-3%29%2Bx=3


that is, plot y=3

on the same graph you see that the only

solution is the x-coordinate of the point

where they intersect. 




They intersect only at (2,3). The x-coordinate
of that point is 2, so x=2 is the only
solution to the system.  But we wonder why we
got the extraneous solution.

We now notice that the curve of the left
side is really part of a slanted parabola,
and if we were to draw in the rest of the 
parabola, that is, the part in light blue 
below: 



we can see that the other part of that parabola
does indeed intersect the graph of the right side,
(the green line) at the point (6,3).  But we 
discard x=6 because the curve of the left side
of the original equation does not include the light
blue part of the parabola.

Edwin