Final answer:
The justifications for each step in completing a proof are substitution, induction, contradiction, and direct proof.
Step-by-step explanation:
The justifications for each step in completing a proof are as follows:
- Substitution: In this step, we replace variables or terms with equivalent values or expressions. This is useful to simplify equations or make calculations.
- Induction: Induction is used to prove statements that hold true for all natural numbers. It involves proving a base case and then showing that the statement holds for an arbitrary natural number, assuming it holds for the previous natural number.
- Contradiction: Contradiction is a proof technique that involves assuming the opposite of what we want to prove and showing that it leads to a contradiction. This implies that the original claim must be true.
- Direct Proof: In a direct proof, we use logical steps to show that the hypothesis or assumption directly implies the conclusion. This is a straightforward and direct way of proving a statement.