Question 31·Easy·Equivalent Expressions
Which expression is equivalent to ?
For equivalent-expression questions with products and subtraction, first expand each product carefully using distribution (FOIL), then rewrite the problem as a subtraction of two expanded expressions. Distribute the minus sign to every term in the second expression, then group and combine like terms (quadratic, linear, and constant) in an organized way. If you’re unsure, plug in a simple value for (like or ) into the original expression and each answer choice to quickly eliminate options that do not match.
Hints
Start by expanding products
Ignore the subtraction for a moment and expand and separately using distribution (FOIL).
Be careful with the subtraction
When you subtract , think of it as subtracting each term in that expanded trinomial. How does the minus sign affect each term?
Combine like terms systematically
After distributing the minus sign, group terms together, terms together, and constants together, and then combine each group.
Desmos Guide
Enter the original expression
In one Desmos line, type the full expression: (4x - 3)(x + 2) - (x - 1)(2x + 5) and let Desmos simplify it; note the simplified form that appears on the right.
Compare with each answer choice
On separate lines, enter each choice, for example A(x) = 2x^2 + 8x - 1, B(x) = 6x^2 + 2x - 1, etc., and compare their simplified forms with the simplified form of the original expression. The correct choice is the one whose expression exactly matches the simplified original expression for all .
Step-by-step Explanation
Expand each product separately
First, expand .
- Multiply term by term (FOIL):
- First:
- Outer:
- Inner:
- Last:
Combine like terms:
Now expand :
- First:
- Outer:
- Inner:
- Last:
Combine like terms:
Rewrite the whole expression using the expanded products
Substitute the expanded forms back into the original expression:
becomes
Now the problem is to simplify this difference of two trinomials.
Distribute the subtraction and combine like terms
Distribute the minus sign to every term in the second parentheses:
Now combine like terms:
- terms:
- terms:
- Constant terms:
So the simplified expression is:
which matches answer choice D.