Math 1 · Unit 3 · Lesson 2 · part 5 of 8
Match it to the graph: pick the one that fits, by elimination
Now the payoff of reading m and b.
Match it to the graph: pick the one that fits, by elimination
Now the payoff of reading m and b. On a test you will see one equation and several small graphs, and you have to pick the one that fits. Do not plug in points to find it. Read what the equation forces the graph to do, cross out every graph that breaks a rule, and check the one that is left.
- 1The sign of m: which way does it go?A negative m falls from left to right. A positive m climbs. An m of 0 is a flat horizontal line. Cross out every graph that goes the wrong way.
- 2b: where does it cross the y-axis?The line has to cross the y-axis at (0, b). Cross out any graph still standing that crosses somewhere else. That usually leaves one.
- 3The size of m: steep or gentle?If two are still standing, a large slope is steep and a small one is gentle. That breaks the tie.
Worked: y = −2x + 3
Four graphs: A climbs and crosses at 3. B falls and crosses at −3. C falls steeply and crosses at 3. D falls gently and crosses at 3.
Look 1: m = −2 is negative, so the line falls. Cross out A. Look 2: b = 3, so it crosses at (0, 3). Cross out B. Look 3: a slope of size 2 is steep. Cross out D. C is left.
Write the answer with the rules
Not just a letter. Say what ruled out each wrong choice: A climbs, but our slope is negative. B crosses at −3, but b is 3. D is gentle, but the size of m is 2. Then, if you want, plug in one point as a final double-check, never as the way to find the answer.
Three to try. Each card has one equation and four small graphs; the dot marks where each graph crosses the y-axis. Pick the one that fits, then read the feedback to see the rule that ruled out each of the others.