Question 70·Easy·Nonlinear Equations in One Variable; Systems in Two Variables
What is one possible value of that satisfies the equation?
For absolute value equations of the form , first make sure the absolute value expression is isolated on one side. Then immediately split it into two linear equations: and . Solve each quickly using standard linear steps (subtract, then divide), and check both solutions in the original equation if you have time. On the SAT, write down both possible values and then select or grid in any value that satisfies the problem’s instructions.
Hints
Use the definition of absolute value
Think about what means in general. What two values can have if its absolute value is 7?
Split into two cases
Rewrite as two separate equations without the absolute value bars. One equation sets equal to 7, and the other sets equal to the opposite of 7.
Solve both simple equations
Once you have the two linear equations, solve each one step by step: first subtract 1 from both sides, then divide by 3. Each equation will give you a possible value of .
Check your solutions
After you find the possible values of , plug them back into to verify that the result is indeed 7.
Desmos Guide
Enter the two sides as separate graphs
In Desmos, type y = |3x + 1| on one line and y = 7 on another line so you can see where the graphs intersect.
Find the intersection points
Look for the points where the V-shaped graph of crosses the horizontal line . Tap or click on each intersection; Desmos will show the coordinates of those points.
Read off the x-values
The -coordinates of the intersection points are the solutions to . Either of those -values is a valid value of for the equation.
Step-by-step Explanation
Understand the absolute value equation
The equation is
Absolute value means distance from 0. So says that the expression is 7 units away from 0 on the number line. That can happen in two ways: can be 7 or .
Set up the two linear equations
From , write the two possible cases:
- Case 1:
- Case 2:
Each case is now a simple linear equation in .
Solve each linear equation for z
Solve each case separately:
For Case 1:
For Case 2:
Now divide each equation by 3 to isolate .
Find the possible values of z and choose one
Divide both sides of each equation by 3:
- From , we get .
- From , we get .
Both and make true. The question asks for one possible value of , so you can give as a correct answer.