Mistake Master

Connecting Multiple Representations of Limits AB & BC

A limit can be presented as a graph, a table, a formula, or a sentence, and fluency means moving freely among them. A cancelled factor in the algebra is a hole in the graph. A surviving denominator factor is an asymptote. A two-sided table closing on one value is the sentence "as $x$ approaches $a$ from either side, $f(x)$ approaches $L$". Each view makes something different easy: the graph shows behavior, the algebra gives exact values, the table shows convergence happening.

Because the views are redundant, disagreement between them is a reliable error signal, and the errors it catches are the unit's usual ones. A table that reports a limit where the graph shows a jump was sampled on one side only. An answer that reports the function value rather than the limit shows up as a mismatch between the plotted dot and the traced height. And a graph read too precisely, or a table stopped too early, will disagree with the algebra that settles the question exactly.

ALGEBRAIC (x² − 4)/(x − 2) = x + 2, x ≠ 2 limit = 4 GRAPHICAL a line with a hole NUMERICAL 1.99 → 3.99 2.01 → 4.01 closing on 4 VERBAL as x approaches 2 from either side, f(x) approaches 4 the cancelled factor, the hole, and the converging columns are the same fact
Four descriptions of one object. A correct answer survives all four translations.
TABLE SAYS 2.1 → 4.1 2.01 → 4.01 "limit is 4" GRAPH SAYS a jump: no limit who is right? the graph. every sampled input was > 2 disagreement between views is an error signal, and it names the error
The views cannot actually conflict. When they seem to, one reading is wrong, and here it is the sampling.

The work

3 ways in · any order
Lesson
Connecting Multiple Representations of Limits

Translating a limit among graph, table, formula, and sentence, what each view is authoritative about, and how to use disagreement between them as an error check.

Skill check · 10 scenarios
Diagnostic
10-item topic check

Ten items spanning the three failure modes of this topic: reporting a function value as a limit, ignoring one side at a join, and misreading a graph or table. Take it cold to find which one is yours, or after the lesson to confirm it is not.

Not yet available · 10 items
Targeted Practice
Drill a single misconception

Pick one of the failure modes you missed and drill it on its own. The round is adaptive: two correct in a row clears the misconception and moves you to the next.

Take the diagnostic to identify your misconceptions