Signs at the Posts, Boundaries In or Out

You'll learnto catch signs at predictable posts and decide whether an endpoint is in or out.

Signs go missing at a few predictable posts and boundaries get counted wrong at the edges; the fix is to slow down at those exact spots — squaring a negative, distributing a minus, and deciding whether an endpoint is in or out.

8 STEPS · 6 QUICK CHECKS · watch the sign posts · count the endpoints · v2

signs · boundaries

Before you start

What you're looking at

A number line from −5 to 4 with an open dot at −3 and a filled dot at 2, beside two preview cards.

The question

Which integers fall inside the interval, and does each endpoint count?

Watch for

Watch the open endpoint stay out and the filled one count in; the edges decide the total.

What the symbols mean

An open dot is excluded, a filled dot included; the cards preview the sign posts and boundary reads.

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