Systems: Elimination and Systems: No or Infinite Solutions | Six Minutes: SAT Math, Part 7

Six Minutes: SAT Math, Part 7: Systems: Elimination and Systems: No or Infinite Solutions: Add or subtract to cancel a variable; then Systems: No or Infinite Solutions Learn the elimination method for two-variable linear systems: match one pair of coefficients, then add or subtract to cancel. Includes a fully worked example checked a second way and the classic add-versus-subtract trap. Then: Count solutions to a 2x2 linear system by comparing slopes and intercepts. Match coefficient ratios to find missing constants for no-solution or infinite-solution cases. Chapters 0:00 Introduction 0:22 The idea 0:45 Why it beats substitution 0:59 Worked example 1:45 The trap 2:03 Recap 2:27 The idea 2:55 Compare the two lines 3:31 Find the missing number 3:59 Worked example 5:10 Trap 5:27 Recap 5:43 Thanks for watching Practice problems 1. Solve the system 5x + 2y = 21 and 3x - 2y = 3. (Answer: x = 3, y = 3) 2. Solve the system 2x + 3y = 12 and 4x + 3y = 18. (Answer: x = 3, y = 2) 3. For what value of c does the system 2x + 5y = 7 and 4x + cy = 14 have infinitely many solutions? (Answer: c = 10, since all ratios equal 2.) 4. For what value of c does the system 2x + 5y = 7 and 4x + cy = 3 have no solution? (Answer: c = 10, same slope but constants 7 and 3 differ.) Six Minutes @SixMinuteClass: One technique, about six minutes. The narrator's voice is synthetic (computer-generated). Independent educational video. Not affiliated with or endorsed by the College Board. © 2026 Six Minutes · @SixMinuteClass