Casio fx-CG50 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.
From the MAIN MENU, open Graph (icon 5) and type the function on Y1: . Press to register it.
Frame the graph on the standard window: (V-Window) → (STANDRD), then and (DRAW). 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 guarantee there is only one root.
Widen the x-range just enough to check the right side: press (Zoom) → (OUT), then repeat (Zoom) → (OUT) once more. With the default factor 2, the x-window goes [−10,10]→[−20,20]→[−40,40], which is wide enough to include the second root near x≈33.1. The y-range widens as well, so the graph gets squashed close to the x-axis.
Crop back in with a box: press (Zoom) → (BOX). Anchor one corner above-left of the curve's strip with , move below-right (keeping both crossings inside the marquee), and press again. The window snaps to the box, keeping the full x-coverage with a readable y-scale.
Press (G-Solv) → (ROOT). The Casio solves every root in the current window and steps through them in order from left to right; the screen shows one at a time, and you move between them with the / cursor.
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.