SOLUTION: solve this equation by using the quadratic form 3/x-7+4/x+2=1

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Question 464128: solve this equation by using the quadratic form
3/x-7+4/x+2=1

Found 2 solutions by Alan3354, Edwin McCravy:
Answer by Alan3354(69443) About Me  (Show Source):
You can put this solution on YOUR website!
solve this equation by using the quadratic form
3/x-7+4/x+2=1
3/x + 4/x -7 + 2 = 1
7/x - 5 = 1
7/x = 6
x = 7/6
--------
The formula wasn't needed.
If you meant something else, make it clear an unambiguous.

Answer by Edwin McCravy(20054) About Me  (Show Source):
You can put this solution on YOUR website!

The other tutor took your equation to be

3%2Fx-7%2B4%2Fx%2B2=1

because you didn't put parentheses around denominators to show
where they start and where they end.  When you write algebra 
fractions all on one line, using a foward slash "/" for a fraction
bar, you must put parentheses around both entire numerators and
entire denominators any time there is more than just one letter 
or just one number in the numerator or denominator.  Otherwise
there is no way to know where numerators and denominators start 
and end.  And when you don't put the parentheses in, it is 
understood that the numerator or denominator consists of just 
the one number or the one letter which is closest to the forward 
slash "/".  That's the way the other tutor interpreted your
equation.

I believe you intended for your equation to be this:

3%2F%28x-7%29%2B4%2F%28x%2B2%29=1

which you should have written all on one line as

3/(x-7)+4/(x+2)=1

That way we can tell that the -7 and +2 are parts of the 
denominators and not separate terms.  It was not necessary
to place parentheses around the numerators because they
just consist of one number each, 3 and 4, but it was necessary 
to put parentheses around the denominators.

Assuming you meant this:

3%2F%28x-7%29%2B4%2F%28x%2B2%29=1,

write the 1 as 1%2F1 so everything will be a fraction:

3%2F%28x-7%29%2B4%2F%28x%2B2%29=1%2F1

The LCD is (x-7)(x+2) so we multiply through by red%28expr%28%28%28x-7%29%28x%2B2%29%29%2F1%29%29  




Then we cancel away the denominators:



We end up with no fractions at all

3%28x%2B2%29%2B4%28x-7%29=%28x-7%29%28x%2B2%29

Remove the parentheses:

3x%2B6%2B4x-28=x%5E2-5x-14

Collect like terms:

7x-22=x%5E2-5x-14

Get 0 on the left:

0=x%5E2-12x%2B8

Swap sides:

x%5E2-12x%2B8=0

Compare to 

ax%B2%2Bbx%2Bc=0

And see that a=1, b=-12 and c=8.

Then use

x+=+%28-b+%2B-+sqrt%28+b%5E2-4%2Aa%2Ac+%29%29%2F%282%2Aa%29+ 

 

x+=+%2812+%2B-+sqrt%28144-32+%29%29%2F2+

 x+=+%2812+%2B-+sqrt%28112+%29%29%2F2+

x+=+%2812+%2B-+sqrt%2816%2A7%29%29%2F2+

x+=+%2812+%2B-+4sqrt%287%29%29%2F2+

Factor 4 out of the top:

x+=+%284%283+%2B-+sqrt%287%29%29%29%2F2+

Divide top and bottom by 2

x+=+2%283+%2B-+sqrt%287%29%29+

or if you prefer:

x+=+6+%2B-+2sqrt%287%29%29+

The two exact solutions are

6+%2B+2sqrt%287%29%29+ and 6+-+2sqrt%287%29%29+

They are approximately 0.7 and 11.3.

Edwin