To establish the correct sequence of steps in the proof that the sum \( t = r + s \) is irrational when both \( r \) and \( s \) are rational, we should follow a logical progression that begins with an assumption and leads to a contradiction.
- Step 2: For a contradiction, assume that \( t \) is rational, and write \( r \) and \( t \) as fractions.
- Step 4: Find a common denominator.
- Step 1: Subtract, writing \( s \) as a fraction.
- Step 3: Realize a contradiction.
So the correct sequence is:
Step 2, Step 4, Step 1, Step 3
This corresponds to the option: Step 2, Step 4, Step 1, Step 3.