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How to find the zeros of a function on a TI-84 Plus CE, TI-84 Plus or TI-83 Plus

By E-Code · updated

Graph the function, press 2nd CALC (above TRACE) and 2 for zero, then type a left bound, ENTER, a right bound, ENTER, and ENTER at Guess. The calculator shows the X where the graph crosses the x-axis.

Before you start

Type the function into the Y= editor first: this guide uses Y1 = X² − 4 (Y=, X,T,θ,n, x², −, 4, then 2nd QUIT).

Y= X,T,θ,n X² − 4 2nd MODE

Step by step

  1. Draw the graph. GRAPH Press GRAPH. Y1 = X² − 4 is already typed in for you.
  2. Open CALC. 2nd TRACE Press 2nd, then TRACE. CALC (written above TRACE) holds the graph tools.
  3. Pick zero. 2 Press 2 for zero. It asks for a left bound: an X to the left of the crossing.
  4. Left of the crossing. 0 Type 0. The graph is below the x-axis there.
  5. Confirm the left bound. ENTER Press ENTER.
  6. Right of the crossing. 3 Type 3. The graph is above the x-axis there, so it crosses in between.
  7. Confirm the right bound. ENTER Press ENTER. Now it asks for a guess.
  8. Find the zero. ENTER Press ENTER to take the cursor's spot as the guess. The calculator homes in on the crossing.
  9. Read the zero. X = 2, Y = 0: X² − 4 = 0 when X = 2. Do it again with bounds −3 and 0 to find the other root, −2.

What the screen shows

X = 2, Y = 0: X² − 4 = 0 when X = 2. Do it again with bounds −3 and 0 to find the other root, −2.

Look for X=2 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 “Find the zeros of a function” on the TI-84 calculator

Related

Math programs for the TI-84 Plus CE:

All TI-84 algebra guides · All TI-84 guides · All calculator guides