Question 65·Medium·Equivalent Expressions
Which expression is equivalent to ?
For equivalent-expression questions, first simplify the given expression step by step: expand any products, carefully distribute minus signs (especially when subtracting a whole parenthetical), then combine like terms. Avoid doing algebra in your head—write each intermediate step, track signs closely, and only then match your final simplified form to the answer choices. When in doubt, you can also plug in a simple value for (like or ) into both the original expression and each choice to quickly eliminate non-equivalent options.
Hints
Handle the product first
Focus on simplifying before dealing with the rest of the expression. Can you use FOIL or a special product pattern here?
Be careful with the minus sign
After you find , remember there is a minus in front of the parentheses. How does that affect each term inside the parentheses when you rewrite the expression?
Combine like terms at the end
Once everything is written out without parentheses, group terms, terms, and constant terms separately and combine each group.
Desmos Guide
Enter the original expression
In Desmos, type y = (x^2 - 6x + 9) - (x - 3)(x + 3) + 5 to graph the original expression as a function.
Enter each answer choice as a separate function
Type each option as its own function, for example y = -6x + 23, y = -6x - 23, y = 6x + 23, and y = 6x - 23 (one per line).
Compare the graphs
Look to see which of the four lines lies exactly on top of the graph of the original expression for all values of . The choice whose graph coincides perfectly with the original graph is the equivalent expression.
Step-by-step Explanation
Expand the product
Start with the product .
Use FOIL or the difference of squares pattern:
So the original expression becomes
Distribute the subtraction
Now distribute the minus sign across the parentheses .
Subtracting is the same as adding :
Combine like terms to get the final simplified expression
Group like terms:
- The terms: (they cancel).
- The terms: only remains.
- The constants: .
So the entire expression simplifies to
which matches choice A.