Question 16·Easy·Linear Inequalities in One or Two Variables
The inequality
is shown above.
Which of the following inequalities is equivalent to the inequality above?
For inequality-equivalence questions, first simplify the given inequality by factoring out and dividing by any common factors of all terms. Remember that dividing or multiplying by a positive number keeps the inequality direction the same, while doing so by a negative number reverses it. After simplification, rewrite the expression (for example, changing all signs) to match the general form of the answer choices, carefully tracking when the inequality sign should flip, and then choose the option that matches your final equivalent inequality exactly.
Hints
Look for a common factor
All the numbers in are multiples of the same integer. What can you divide all three terms by to simplify the inequality?
Be careful with negative factors
After simplifying once, you may want to change the signs of all the terms. What happens to the inequality sign when you multiply or divide both sides by ?
Match the form of the answer choices
Most answer choices start with a positive term. Once you have a simplified inequality, how can you rewrite it so that it starts with while still remaining equivalent?
Desmos Guide
Graph the original inequality
In Desmos, type the original inequality: -8x + 12y <= 24. You will see a boundary line and a shaded region representing all that satisfy the inequality.
Graph each answer choice for comparison
On separate lines, enter each answer choice exactly as written (for example, 2x - 3y >= -6, 2x - 3y <= -6, etc.). For each one, look at the boundary line and the shaded region.
Identify the equivalent inequality
Compare the graphs: the correct answer will have exactly the same boundary line and shaded region as the graph of -8x + 12y <= 24. Any choice whose shading is on the opposite side of the line or whose line is in a different place is not equivalent.
Step-by-step Explanation
Notice the common factor
The given inequality is
All three terms , , and are multiples of (and also of ). This means we can simplify the inequality by dividing every term by the same nonzero number.
First simplify by a positive factor
To keep track of the inequality sign more easily, start by dividing both sides by (a positive number):
which simplifies to
Dividing by a positive number does not change the direction of the inequality sign.
Rewrite in a more standard form
The simplified inequality is equivalent to the original one, but most of the answer choices are written with a positive term. To turn into , multiply every term in the inequality by :
This will change the signs of all terms.
Account for multiplying by a negative and match the choice
Multiplying by gives
When you multiply or divide an inequality by a negative number, you must reverse the inequality sign, so becomes :
This is the inequality that is equivalent to the original one, so the correct choice is .