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Linear Inequalities — Digital SAT SAT Math revision notes

A 3-page visual revision sheet for Linear Inequalities, written for Digital SAT SAT Math. Formulas, diagrams and the traps that cost marks, laid out to be read the night before rather than the term before. Free, and it opens inside CapCompass.

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Linear Inequalities in one look

solve it like an equation, with one rule that can turn the whole thing around

The rules, and the one that bites

  • adding or subtracting keeps the sign a < b ⇒ a + c < b + c
  • multiplying by a positive keeps it a < b, k > 0 ⇒ ka < kb
  • multiplying by a negative FLIPS it a < b, k < 0 ⇒ ka > kb
  • at least k, no less than k x ≥ k
  • at most k, no more than k x ≤ k

Q. Solve 5 - 3x < 2x + 20.

  1. gather the x terms on the left: 5 - 3x - 2x < 20
  2. 5 - 5x < 20, then subtract 5: -5x < 15
  3. divide both sides by -5, and flip the sign because -5 is negative

Answer: x > -3

Four signs, and the words that hide them

  • greater than: more than, over, exceeds. The boundary is excluded
  • at least: no less than, minimum of, a floor. The boundary counts
  • less than: under, below, fewer than. The boundary is excluded
  • at most: no more than, maximum of, capacity, budget. The boundary counts

Equation vs Inequality

Equation
  • the answer is a single value of x
  • the graph of a two-variable one is a line
  • every legal move keeps the equals sign as it is
Inequality
  • the answer is a whole range of values
  • the graph of a two-variable one is a region on one side of a line
  • dividing by a negative reverses the sign

Page 1 of 3. The full sheet, all 3 pages, opens free in the app.

What this Linear Inequalities sheet covers

Open the full Linear Inequalities sheet →Free, works offline, no account needed. All 3 pages, plus a study plan built around your own exam dates.

How CapCompass uses this sheet

These notes are not a standalone PDF. CapCompass plans SAT Math chapter by chapter against your real exam dates and free hours, and when the plan reaches Linear Inequalities the sheet opens inside the study block itself — at the page covering the sub-topic that block is on, with the timer still running. Revision arrives at the moment the plan says revise, instead of having to be gone looking for.

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