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How to solve simultaneous equations on a TI-84 Plus CE, TI-84 Plus or TI-83 Plus

By E-Code · updated

Open APPS, PlySmlt2, press any key and 2, set EQUATIONS and UNKNOWNS (◀ onto 2, ENTER on each row) and press GRAPH (NEXT). Type each row's numbers with ENTER and press GRAPH (SOLVE): 2x+y=7 and x−3y=−7 give x = 2, y = 3.

Step by step

  1. Open APPS. APPS Press APPS. It lists the apps on your calculator.
  2. Open PlySmlt2. 7 Press 7 for PlySmlt2. On your own calculator its number may differ.
  3. Past the title. ENTER Press any key, here ENTER. The main menu opens.
  4. Simultaneous eqn solver. 2 Press 2. The mode screen asks how many EQUATIONS and UNKNOWNS; both start on 3.
  5. Two equations. ◀ ENTER Press ◀ once onto 2, then ENTER.
  6. Two unknowns. ▼ ◀ ENTER Press ▼ to the UNKNOWNS row, ◀ onto 2, then ENTER.
  7. Press NEXT. GRAPH Press GRAPH, the key under NEXT. The keys under the screen work as its buttons.
  8. Type the numbers. 2 ENTER 1 ENTER 7 ENTER 1 ENTER (-) 3 ENTER (-) 7 ENTER For 2x + y = 7 and x − 3y = −7, type each number and ENTER, row by row: 2, 1, 7, then 1, (−)3, (−)7.
  9. Solve. GRAPH Press GRAPH, now the key under SOLVE.
  10. Every unknown at once. x = 2 and y = 3: 2·2 + 3 = 7 and 2 − 3·3 = −7. Up to 10 equations work the same way; with no single answer, RREF shows why.

What the screen shows

x = 2 and y = 3: 2·2 + 3 = 7 and 2 − 3·3 = −7. Up to 10 equations work the same way; with no single answer, RREF shows why.

Look for y=3 on the screen.

Try it with the keys lit up

This guide is one of E-Code's Learn lessons. Open it on E-Code's TI-84 calculator and each key lights up in turn as you press it.

Try “Solve simultaneous equations” on the TI-84 calculator

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