Question 143·Medium·Nonlinear Equations in One Variable; Systems in Two Variables
The equation above relates the distinct real numbers and with . Which equation correctly expresses in terms of ?
When a question asks you to express one variable in terms of another from a rational equation, treat it like any equation-solving problem: first clear the denominator by multiplying both sides, then distribute, collect all terms with the target variable on one side, and factor it out. After dividing to isolate the variable, carefully handle negative signs and factor out -1 if needed so your expression matches the format of the answer choices. Avoid trying to 'flip' numerators and denominators by pattern; systematic algebra is both faster and less error-prone under test pressure.
Hints
Eliminate the fraction first
You are given . Think about what you can multiply both sides by to get rid of the denominator .
Get all the t-terms together
After you clear the denominator and distribute , rearrange the equation so that all terms involving are on one side and all terms without are on the other side.
Factor and solve for t
Once all t-terms are on one side, factor out from that side. Then divide both sides by the remaining factor to isolate .
Match the form of the answer choices
If you end up with extra negative signs, consider factoring out from the numerator and/or denominator so that your final expression looks like one of the answer choices.
Desmos Guide
Enter the original relationship
In Desmos, define the function of that gives :
Type: f(t) = (5t - 1) / (2t + 3)
This represents the original equation as .
Pick a test value for s and compute t from each option
Choose a simple value for that does not make any denominator zero (for example, or ). In Desmos, define that value (e.g., s = 1). Then, for each answer choice, create an expression for using that value, such as t_A = (5s - 2) / (2 - 3s), t_B = (1 - 3s) / (5 + 2s), etc.
Check which option satisfies the original equation
For each value you computed, evaluate f(t_A), f(t_B), f(t_C), and f(t_D) in Desmos. Compare each result to your chosen value. The correct formula for will be the one where f(t_choice) equals (and will continue to work if you try a second, different value). Match that successful formula with the corresponding answer choice.
Step-by-step Explanation
Clear the denominator
Start with the given equation:
Multiply both sides by to eliminate the denominator:
Now distribute on the left:
Collect the t-terms
We want all the terms involving on one side and the constant/-only terms on the other.
Subtract from both sides and subtract from both sides:
Now factor out of the left side:
Isolate t and simplify signs
Divide both sides by to solve for :
Factor out of the numerator and denominator:
- Numerator:
- Denominator:
So
Thus, the correct expression for in terms of is , which matches choice D.