Proof: Substitute Two Numbers
Let's prove the following theorem:
if the following are true:
- a = b + c
- b = x
- c = y
then a = x + y
Proof:
Given
| 1 | a = b + c |
|---|---|
| 2 | b = x |
| 3 | c = y |
| # | Claim | Reason |
|---|---|---|
| 1 | b + c = x + c | if b = x, then b + c = x + c |
| 2 | x + c = x + y | if c = y, then x + c = x + y |
| 3 | b + c = x + y | if x + c = x + y and b + c = x + c, then b + c = x + y |
| 4 | a = x + y | if b + c = x + y and a = b + c, then a = x + y |
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