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Lesson 2 of 16

One waits, the other claims

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6 min

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The board shows n + 3. Below it is n + 3 = 8. Here n is a letter for a number. They look alike. Only one of them can be true or false.

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n + 3 — no equals sign.
Step 1 of 3
  1. n + 3 — no equals sign.
  2. It waits for a value.
  3. Add = 8. Now it claims something.

What each line is for

n + 3 is an expression. Put 5 in place of n, and n + 3 is 8. Put 20 in place of n, and n + 3 is 23. It claims nothing. It does not say that anything is true.

n + 3 = 8 is an equation. It claims that both sides are the same number. So it can be true or false.

Rule: No equals sign means expression. An equals sign with both sides filled means equation.

An equation needs no letter. 9 + 8 = 17 is an equation, and it is true.

Try the lab to finish this lesson.