Mathematics — first biennium · Lesson
The first principle preserves solutions when you add or subtract the same quantity on both sides. We avoid the shortcut 'move it across and change the sign': first make explicit the operation that preserves balance.
In this lesson: Apply the same addition or subtraction to both members while keeping explicit the operation that preserves balance.
You can already assume: Solution verification and algebraic sums.
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ConceptStep separates what is required from what is recommended or useful as reinforcement. Only required prerequisites block your progress.
Relationships: solid line = required · dashed line = recommended · dotted line = reinforcement.