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+3
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-5/2x = -7/4x-5/6

 Mar 16, 2016

Best Answer 

 #4
avatar
+5

Solve for x:
-5/(2 x) = -5/6-7/(4 x)

-5/(2 x) = -5/(2 x) and -5/6-7/(4 x) = -5/6-7/(4 x):
-5/(2 x) = -5/6-7/(4 x)

Bring -5/6-7/(4 x) together using the common denominator 12 x:
-5/(2 x) = (-21-10 x)/(12 x)

Cross multiply:
-60 x = 2 x (-21-10 x)

Expand out terms of the right hand side:
-60 x = -42 x-20 x^2

Add 20 x^2+42 x to both sides:
20 x^2-18 x = 0

Factor x and constant terms from the left hand side:
2 x (10 x-9) = 0

Divide both sides by 2:
x (10 x-9) = 0

Split into two equations:
x = 0 or 10 x-9 = 0

Add 9 to both sides:
x = 0 or 10 x = 9

Divide both sides by 10:
x = 0 or x = 9/10

-5/(2 x) => -5/(2 0)  =  infinity^~
-5/6-7/(4 x) => -7/(4 0)-5/6  =  infinity^~:
So this solution is incorrect

-5/(2 x) => -5/((2 9)/10)  =  -25/9
-5/6-7/(4 x) => -5/6-7/((4 9)/10)  =  -25/9:
So this solution is correct

The solution is:
Answer: |  x = 9/10

 Mar 16, 2016
 #1
avatar
0

-5/2x = -7/4x-5/6

 

Solve for x:
(-5 x)/2 = -5/6-(7 x)/4

Put each term in -5/6-(7 x)/4 over the common denominator 12: -5/6-(7 x)/4  =  (-10)/12-(21 x)/12:
(-5 x)/2 = (-10)/12-(21 x)/12

(-10)/12-(21 x)/12 = (-10-21 x)/12:
(-5 x)/2 = (-10-21 x)/12

Multiply both sides by 12:
(-5×12 x)/2 = (12 (-10-21 x))/12

12/2 = (2×6)/2 = 6:
-56 x = (12 (-10-21 x))/12

(12 (-10-21 x))/12 = 12/12×(-10-21 x) = -10-21 x:
-5×6 x = -10-21 x

6 (-5)  =  -30:
-30 x = -10-21 x

Add 21 x to both sides:
21 x-30 x = (21 x-21 x)-10

21 x-21 x = 0:
21 x-30 x = -10

21 x-30 x = -9 x:
-9 x = -10

Divide both sides of -9 x = -10 by -9:
(-9 x)/(-9) = (-10)/(-9)

(-9)/(-9) = 1:
x = (-10)/(-9)

The sign of (-10)/(-9) is positive, so (-10)/(-9)  =  1×10/9:
Answer: |  x = 10/9

 Mar 16, 2016
 #3
avatar+1904 
0

Look at my answer. 10/9 is not the correct answer.  The answer is 9/10 or 0.9.

gibsonj338  Mar 16, 2016
 #2
avatar+1904 
+5

\(\frac{-5}{2x}=\frac{-7}{4x}-\frac{5}{6}\)

 

\(-\frac{5}{2x}=-\frac{7}{4x}-\frac{5}{6}\)

 

\((-\frac{5}{2x})\times4x=(-\frac{7}{4x}-\frac{5}{6})\times4x\)

 

\(-\frac{20x}{2x}=(-\frac{7}{4x}-\frac{5}{6})\times4x\)

 

\(-\frac{20x}{2x}=-\frac{28x}{4x}-\frac{20x}{6}\)

 

\(-10=-\frac{28x}{4x}-\frac{20x}{6}\)

 

\(-10=-7-\frac{20x}{6}\)

 

\(-10\times6=(-7-\frac{20x}{6})\times6\)

 

\(-60=(-7-\frac{20x}{6})\times6\)

 

\(-60=-42-\frac{120x}{6}\)

 

\(-60=-42-20x\)

 

\(-60+42=-42-20x+42\)

 

\(-18=-42-20x+42\)

 

\(-18=0-20x\)

 

\(-18=-20x\)

 

\(\frac{-18}{-20}=\frac{-20x}{-20}\)

 

\(\frac{9}{10}=\frac{-20x}{-20}\)

 

\(\frac{9}{10}=\frac{1x}{1}\)  

\(\frac{9}{10}=\frac{x}{1}\)

 

\(\frac{9}{10}=x\)

 

\(0.9=x\)

 

\(x=0.9\)

.
 Mar 16, 2016
edited by gibsonj338  Mar 16, 2016
edited by gibsonj338  Mar 16, 2016
 #4
avatar
+5
Best Answer

Solve for x:
-5/(2 x) = -5/6-7/(4 x)

-5/(2 x) = -5/(2 x) and -5/6-7/(4 x) = -5/6-7/(4 x):
-5/(2 x) = -5/6-7/(4 x)

Bring -5/6-7/(4 x) together using the common denominator 12 x:
-5/(2 x) = (-21-10 x)/(12 x)

Cross multiply:
-60 x = 2 x (-21-10 x)

Expand out terms of the right hand side:
-60 x = -42 x-20 x^2

Add 20 x^2+42 x to both sides:
20 x^2-18 x = 0

Factor x and constant terms from the left hand side:
2 x (10 x-9) = 0

Divide both sides by 2:
x (10 x-9) = 0

Split into two equations:
x = 0 or 10 x-9 = 0

Add 9 to both sides:
x = 0 or 10 x = 9

Divide both sides by 10:
x = 0 or x = 9/10

-5/(2 x) => -5/(2 0)  =  infinity^~
-5/6-7/(4 x) => -7/(4 0)-5/6  =  infinity^~:
So this solution is incorrect

-5/(2 x) => -5/((2 9)/10)  =  -25/9
-5/6-7/(4 x) => -5/6-7/((4 9)/10)  =  -25/9:
So this solution is correct

The solution is:
Answer: |  x = 9/10

Guest Mar 16, 2016
 #5
avatar
0

-5/2x = -7/4x - 5/6

+7/4x   +7/4x

-3/2x = -5/6

+3/2     +3/2

      x = 1.16

 Mar 16, 2016
 #6
avatar+1904 
0

In order to add or subtract fractions the numerators have to be the same bfore you can add or subtract. The actual answer is x=9/10 or x=0.9.

gibsonj338  Mar 16, 2016

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