Lesson 6 of 15
Terms of the same kind
Show on a big screenSort coins: fives with fives, twos with twos. Then count each pile.
3a and 5a — same letter part, a. Step 1 of 3
3aand5a— same letter part,a.- Join them:
8a. 2bstays alone — a different letter part.
Rule: an expression is built from terms, joined by + and −. Two terms are like terms when their letter part matches. Only like terms may be collected. Collected means joined into one term. The letter part of 3a is a.
3a + 5a is 3 lots of a and 5 lots of a. That is 8 lots, so it collects to 8a. 3a + 2b stays as it is — the letters differ.
A plain number has no letter. Plain numbers are like terms too. 3 + 5 collects to 8.
Watch out!
3a + 2b is not 5a. Check at a = 2, b = 3. 3a + 2b gives 6 + 6 = 12. 5a gives 10. Terms with different letters stay separate.
Take two terms at a time. Can they join?
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Try the lab to finish this lesson.