Question 7·Easy·Linear Inequalities in One or Two Variables
The inequality
is given above.
Which of the following inequalities is equivalent to the inequality above?
For “equivalent inequality” questions, keep the inequality balanced by performing the same operation on both sides, just as you would with an equation, but always remember: multiplying or dividing by a negative number flips the inequality sign. Aim to isolate a simple expression (like ) or get the inequality into a standard form, then match it directly to the answer choices. If unsure, you can quickly test one or two easy points (like or ) to see which choices behave differently from the original.
Hints
Focus on the structure of the inequality
Look at the expression inside the parentheses. How is being changed by the ? What operation connects them?
Undo the multiplication by -4
Think about what operation will isolate on the left side. What should you do to both sides of the inequality?
Be careful with the inequality sign
When you divide or multiply an inequality by a negative number, what must you do to the inequality sign? Keep that in mind when simplifying.
Compare your simplified form to the choices
Once you have an inequality in terms of alone, match its sign ( or ) and constant term with the answer choices.
Desmos Guide
Graph the original inequality
In Desmos, enter the inequality -4(2x + y) <= 8. You will see a shaded region representing all pairs that satisfy the original inequality.
Graph each answer choice one by one
On separate lines, enter each choice (for example, 2x + y <= -2, -2x - y >= 2, etc.). For each one, compare its shaded region to the region from the original inequality.
Identify the matching region
The correct choice is the one whose shaded region exactly overlaps the region from -4(2x + y) <= 8—no extra points and no missing points. Read off which inequality that is from your Desmos list.
Step-by-step Explanation
Understand what “equivalent inequality” means
Two inequalities are equivalent if they have exactly the same solution set. That means any pair that makes the original inequality true must also make the new one true, and vice versa.
So our goal is to simplify the given inequality without changing its solutions.
Write the original inequality and simplify inside
Start with the given inequality:
First, you can distribute or go directly to isolating the expression in parentheses. Let's isolate by undoing the multiplication by .
Divide both sides by -4 and flip the inequality
The expression is being multiplied by , so divide both sides by :
When you divide both sides of an inequality by a negative number, you must reverse (flip) the inequality sign from to .
Now simplify each side:
- Left side:
- Right side:
Write the simplified inequality and match it to a choice
After dividing and simplifying, you get:
Now compare this to the answer choices and select the one that matches exactly: , which is choice D.