Removing grouping symbols: Level 2 The relationship of a − b to b − a We know the relationship of a + b to b + a. They are equal. a + b = b + a. But what is the relationship of a − b to b − a ? a − b is the negative of b − a. a − b = −(b − a). For example, 5 − 8 = −(8 − 5). (Compare Lesson 2.) Problem 19. Prove: a − b = −(b − a). To see the answer, pass your mouse over the colored area.
Solution 2. See Lesson 2, Problem 9.
to −1.
We may interpret that rule (Lesson 4) to mean: In any fraction we may change the signs
q − p is the negative of p − q. Problem 21. Apply that rule.
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