TI-84 Plus CE field manual for IB Math
Finding roots of a function
Plot a function, widen the x-window until every x-intercept is on screen, then use the calculator's root / zero tool to read each solution.
Find every root of y=ln(x+2)−12x−0.8.
Press and type the function on Y1: .
Start on the standard window: press (6: ZStandard). One root is visible near x≈0.278, but the graph is still above the x-axis at the right edge of the screen, so this view is too narrow to be sure there is only one root.
Widen the view to check the right side: press (3: Zoom Out) and then once. With the default factor 4, the window expands from [-10,10] to [-40,40], wide enough to reveal the second crossing near x≈33.1. The downside is the y-range also expands, squashing the curve against the x-axis.
Crop back in with a box: press (1: ZBox). Anchor one corner above-left of the curve's strip with , then move below-right (keeping both crossings inside the marquee) and press again. The window snaps to the box, keeping the full x-coverage but restoring a readable y-scale.
Read off the near root: press (2: zero). At Left Bound? move just left of the crossing and press ; at Right Bound? move just right of it and press ; at Guess? move near the crossing and press . The calculator jumps to the zero and prints its coordinates.
Repeat CALC (2: zero) for the second root, the crossing on the right side of the screen. Bracket it the same way: left bound, right bound, then guess.
The roots are approximately x≈0.278 and x≈33.1.
Your turn
Work each one on your calculator, then check the answer.
- 1
Find all real roots of f(x)=x3−4x+1.
- 2
Find all real roots of f(x)=ex−3x2.
- 3
Find all real roots of f(x)=ln(x+3)−x2.