The correct sequence of the steps to prove that the sum \( t = r + s \) is irrational if both \( r \) and \( s \) are irrational can be identified as follows:
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Step 2: For a contradiction, assume that \( t \) is rational, and write \( r \) and \( t \) as fractions.
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Step 4: Find a common denominator.
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Step 1: Subtract, writing \( s \) as a fraction.
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Step 3: Realize a contradiction.
Thus, the correct order is Step 2, Step 4, Step 1, Step 3.