Thread: Quick Check of Solving Equations?

1. Quick Check of Solving Equations?

Could somone please look over this equation and check for errors.

$\displaystyle (X+3)/4-(X-4)/2=3/8$
$\displaystyle (2)(X+3)/4-(4)(X-4)/2=3/8$
$\displaystyle (2x+6-4x-16)/8=3/8$
$\displaystyle (-2X-10)/8=3/8$
$\displaystyle 8((-2X-10)/8=3/8)$
$\displaystyle -2x-10=3$
$\displaystyle -2x=13$
$\displaystyle X=7.5$

2. sorry, this was wrong, check out my solution below.

3. Hmm..not seeing where I went wrong...

I got a common denominator and then simplified..could you show me how you did it?

4. Originally Posted by EddieG
Could somone please look over this equation and check for errors.

$\displaystyle (X+3)/4-(X-4)/2=3/8$
$\displaystyle (2)(X+3)/4-(4)(X-4)/2=3/8$ Mr F says: You have the wrong denominators here. It should be $\displaystyle {\color{red}(2)(X+3)/{\color{blue}8} -(4)(X-4)/{\color{blue}8} = 3/8}$. The next line seems to have used the correct denominators.

$\displaystyle (2x+6-4x {\color{blue}-} 16)/8=3/8$ Mr F says: The first mistake (excluding mistakes in setting out - see above) is in blue. The blue minus should be a plus. This will affect all that follows.

[snip]
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5. Oh sorry, my mistake. My first post was wrong.

this is my solution.

$\displaystyle \frac{x+3}{4} - \frac{x-4}{2} = \frac{3}{8}$

i then multiply the equation by their LCD which is 8.

$\displaystyle [ \frac{x+3}{4} - \frac{x-4}{2} = \frac{3}{8} ] 8$

thus removing the denominators. then it becomes

$\displaystyle 2(x+3) - 4(x-4) = 3$

$\displaystyle (2x+6) - (4x-16) = 3$

$\displaystyle 2x + 6 - 4x + 16 = 3$

$\displaystyle -2x + 22 = 3$

$\displaystyle -2x = -19$

$\displaystyle x = \frac {19}{2}$

$\displaystyle x = 9.5$