Question 105·Hard·Equivalent Expressions
The rational expression
is equivalent to , where and are constants.
What is the value of ?
(Express the answer as an integer)
For equivalent expression questions with rational expressions, first look for common factors in the numerator and denominator instead of expanding everything. Factor out any shared binomials so you can cancel them, then simplify the remaining expression by combining like terms. Once you have a simpler form (like ), carefully match coefficients and constants to the symbols in the question and compute only what is asked (here, ), watching signs to avoid small arithmetic errors.
Hints
Look for a common factor in the numerator
Both terms in the numerator are multiplied by . How can you factor the numerator to take advantage of that?
Simplify before expanding everything
After you factor out the common in the numerator, what happens when you divide by in the denominator?
Handle the subtraction of polynomials carefully
When you subtract from , remember that the minus sign distributes to every term in the second parentheses.
Connect the simplified expression to p and q
Once you have a linear expression of the form , match with and with , then compute .
Desmos Guide
Enter the given rational expression
Type the full expression into Desmos as a function, for example:
Then create a table for (click the gear icon and "Convert to table") to see values such as and .
Use function values to find p − q
Since the simplified form is , note that and . From your table values, compute and then . Use your Desmos values for and to get the numerical value of .
Step-by-step Explanation
Factor the numerator using the common binomial
Look at the numerator:
Both terms share a common factor of , so factor it out:
Now the whole expression becomes
For , the in the numerator and denominator cancel, leaving just the bracketed expression.
Subtract the quadratic expressions carefully
After canceling , you have
Distribute the minus sign over the second parentheses:
Now combine like terms:
- (the terms cancel),
- ,
- . So the simplified expression is
This matches the form with specific values of and .
Identify p and q and compute p − q
From the simplified expression :
- is the coefficient of , so ,
- is the constant term, so . Now compute
So, the value of is 74.