SOLUTION: Solve the following equation for ‘x’ and check for extraneous solutions: {{{sqrt(4-x) - sqrt(x+6) =2}}}

Algebra ->  Circles -> SOLUTION: Solve the following equation for ‘x’ and check for extraneous solutions: {{{sqrt(4-x) - sqrt(x+6) =2}}}      Log On


   



Question 370486: Solve the following equation for ‘x’ and check for extraneous solutions:

sqrt%284-x%29+-+sqrt%28x%2B6%29+=2

Answer by Edwin McCravy(20054) About Me  (Show Source):
You can put this solution on YOUR website!
sqrt%284-x%29+-+sqrt%28x%2B6%29+=2

Isolate one of the radical terms:

sqrt%284-x%29+=2%2B+sqrt%28x%2B6%29

Square both sides:

%28sqrt%284-x%29%29%5E2+=%282%2B+sqrt%28x%2B6%29%29%5E2

Take away the radical and square on the left.
Write expression squared on the right as multiplied by itself:

4-x+=%282%2B+sqrt%28x%2B6%29%29%282%2Bsqrt%28x%2B6%29%29

Use FOIL on the right:

    F  O    I    L 
4-x+=4%2B+2sqrt%28x%2B6%29%2B2sqrt%28x%2B6%29%2B+%28sqrt%28x%2B6%29%29%5E2%29

Simplify:

4-x+=4%2B+4sqrt%28x%2B6%29%2B+%28x%2B6%29

4-x+=4%2B+4sqrt%28x%2B6%29%2B+x%2B6

4-x+=+10%2B+4sqrt%28x%2B6%29%2B+x

Isolate the radical term:

-6-2x+=+4sqrt%28x%2B6%29

Divide all three terms by -2

3%2Bx+=+-2sqrt%28x%2B6%29

Square both sides:

%283%2Bx%29%5E2+=+%28-2sqrt%28x%2B6%29%29%5E2

Write expression squared on the left as multiplied by itself 
Take away the radical and square on the right. 
Don't forget to square the -2 on the right as +4

%283%2Bx%29%283%2Bx%29+=+4%28x%2B6%29

Use FOIL on the left, distribute on the right side:

9%2B3x%2B3x%2Bx%5E2+=+4x%2B24

Simplify

9%2B6x%2Bx%5E2+=+4x%2B24

Get 0 on the right

x%5E2%2B2x-15=+0

Factor

%28x%2B5%29%28x-3%29=+0

Use zero-factor principle:

x%2B5=0 gives x=-5

x-3=0 gives x=3

Test x=-5 in the original equation to see if it 
is a correct solution or an extraneous one:

sqrt%284-x%29+-+sqrt%28x%2B6%29+=2

sqrt%284-%28-5%29%29+-+sqrt%28%28-5%29%2B6%29+=2

sqrt%284%2B5%29+-+sqrt%28-5%2B6%29+=2

sqrt%289%29+-+sqrt%281%29+=2

3-1=2

2=2

That checks, so x=-5 is a correct solution.

Test x=3 in the original equation to see if it 
is a correct solution or an extraneous one:

sqrt%284-x%29+-+sqrt%28x%2B6%29+=2

sqrt%284-%283%29%29+-+sqrt%28%283%29%2B6%29+=2

sqrt%284-3%29+-+sqrt%283%2B6%29+=2

sqrt%281%29+-+sqrt%289%29+=2

1-3=2

-2=2

That does not check, so x=3 is an extraneous solution and
must be discarded.

The only solution is x=-5

Edwin