Spotting a rule is not the same as proving it

Three numbers: 5, 8, 11. Add 3 each time and the next number is 14. But is that the only rule that fits?

You cannot know from three numbers alone. Both rules matched the first three numbers perfectly.

Checking further can help. A fourth number, or a reason the rule should hold. Both help you trust a guess.

Try the lab to finish this lesson.