Paul's Online Notes
Paul's Online Notes
Home / Algebra / Solving Equations and Inequalities / Linear Equations
Show Mobile Notice Show All Notes Hide All Notes
Mobile Notice
You appear to be on a device with a "narrow" screen width (i.e. you are probably on a mobile phone). Due to the nature of the mathematics on this site it is best viewed in landscape mode. If your device is not in landscape mode many of the equations will run off the side of your device (you should be able to scroll/swipe to see them) and some of the menu items will be cut off due to the narrow screen width.

Section 2.2 : Linear Equations

3. Solve the following equation and check your answer.

\[\frac{{4 - 2z}}{3} = \frac{3}{4} - \frac{{5z}}{6}\]

Show All Steps Hide All Steps

Start Solution

The first step here is to multiply both sides by the LCD, which happens to be 12 for this problem.

\[\begin{align*}12\left( {\frac{{4 - 2z}}{3}} \right) & = 12\left( {\frac{3}{4} - \frac{{5z}}{6}} \right)\\ 12\left( {\frac{{4 - 2z}}{3}} \right) & = 12\left( {\frac{3}{4}} \right) - 12\left( {\frac{{5z}}{6}} \right)\\ 4\left( {4 - 2z} \right) & = 3\left( 3 \right) - 2\left( {5z} \right)\end{align*}\] Show Step 2

Now we need to find the solution and so all we need to do is go through the same process that we used in the first two practice problems. Here is that work.

\[\begin{align*}4\left( {4 - 2z} \right) & = 3\left( 3 \right) - 2\left( {5z} \right)\\ 16 - 8z & = 9 - 10z\\ 2z & = - 7\\ z & = - \frac{7}{2}\end{align*}\] Show Step 3

Now all we need to do is check our answer from Step 2 and verify that it is a solution to the equation. It is important when doing this step to verify by plugging the solution from Step 2 into the equation given in the problem statement.

Here is the verification work.

\[\begin{align*}\frac{{4 - 2\left( { - \frac{7}{2}} \right)}}{3} & \mathop = \limits^? \frac{3}{4} - \frac{{5\left( { - \frac{7}{2}} \right)}}{6}\\ \frac{{4 + 7}}{3} & \mathop = \limits^? \frac{3}{4} - \frac{{ - \frac{{35}}{2}}}{6}\\ \frac{{11}}{3} & \mathop = \limits^? \frac{3}{4} + \frac{{35}}{{12}}\\ \frac{{11}}{3} & = \frac{{11}}{3}\hspace{0.2in} {\mbox{OK}}\end{align*}\]

So, we can see that our solution from Step 2 is in fact the solution to the equation.

Note that the verification work can often be quite messy so don’t get excited about it when it does. Verification is an important step to always remember for these kinds of problems. You should always know if you got the answer correct before you check the answers and/or your instructor grades the problem!