Add and subtract signed numbers and explain the meaning of the sign changes.
Choose a smart strategy for signed operations
Problem
Consider these strategies for finding \(-9~-~(-4)\): A, rewrite subtraction as addition; B, compare magnitudes before rewriting; C, move left; D, add the negative. Choose the appropriate strategy, then give the value.
Big Picture
What this problem is really about
Rewrite the subtraction before comparing magnitudes or deciding a direction. Subtracting a negative means adding its positive opposite, which turns the expression into a familiar opposite-sign sum. From the negative starting value, that positive addition moves toward zero; the remaining distance and sign determine the value and confirm the appropriate strategy.
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