Question 56·Medium·Equivalent Expressions
Which of the following is equivalent to the expression above?
For expression-equivalence questions with fractions and parentheses, first distribute the factors into each set of parentheses, then remove parentheses by carefully applying any minus signs to every term. After that, combine like terms by finding common denominators for fractional coefficients and constants. If you are unsure, you can quickly plug in an easy value like or into the original expression and into each choice to see which one always gives the same result.
Hints
Start by expanding
First, expand each product: distribute over and over before worrying about the subtraction.
Watch the minus sign
After you expand, pay close attention to the minus sign in front of the second parentheses. How does subtracting affect the signs of and ?
Combine like terms with fractions
You will have two -terms and two constant terms, all involving fractions. Use a common denominator to combine the -terms, and then add the constants.
Desmos Guide
Graph the original expression
In Desmos, on one line type the original expression:
(5/6)*(3x+2) - (2/3)*(x-4)
This will graph the line that represents the given expression.
Graph each answer choice
On four new lines, type each choice as a separate expression, for example:
(11/6)x - 13/3, (1/6)x + 13/3, (11/6)x + 5/3, and (11/6)x + 13/3.
Each one will appear as its own line on the graph.
Compare the graphs
Compare the graphs: the choice whose line lies exactly on top of the graph of the original expression for all values of is the equivalent expression.
Step-by-step Explanation
Distribute the fractions
Distribute each fraction across its parentheses using the rule .
- First group: .
- Second group: .
So the expression becomes .
Remove the parentheses with the minus sign
Remove the parentheses around the second group. Because there is a minus sign in front, you must change the sign of each term inside.
We have .
So the whole expression is .
Combine like terms
Combine like terms.
First combine the -terms:
.
Use a common denominator of 6: and , so .
Then combine the constants: .
So the simplified expression is , which matches choice D.