GDC workflow: graph, intersect, read
Big idea: Technology helps you find the intersection accurately.
Your job is to enter the graphs correctly, choose the intersection tool, and report the answer in the form the question wants.
| Step | What to do |
|---|---|
| 1 | Enter the first equation as Y₁ |
| 2 | Enter the second equation as Y₂ |
| 3 | Graph both equations |
| 4 | Open the intersect tool |
| 5 | Answer First curve?, Second curve?, Guess? |
| 6 | Read and round the answer correctly |
GDC walkthrough
Step through the exact calculator keystrokes, screen by screen, in study mode.
What IB wants: If the question asks for the solution of simultaneous equations, give the coordinate point.
If it asks you to solve one equation graphically, give the x-values.
IB-style question — solve an equation with the GDC [4 marks]
Use technology to solve the equation 3x + 4 = 0.5x² + 1, giving your answers correct to three significant figures.
Step by step
- Enter each side as its own graph so you can use the intersect tool.
- A parabola and a line meet in at most two points, so run 5:intersect at each crossing.
- The calculator gives the two x-values; round each to 3 significant figures.
Final answer
x = 6.87 or x = −0.873 (3 s.f.). Because the question asks to solve the equation, give the x-values only.
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Choosing a good viewing window
If you cannot see it, you cannot solve it: A poor graph window can hide the intersection or make the graph too squashed to read accurately.
| Problem on screen | What to try |
|---|---|
| Graphs are cut off | Widen the x-range or y-range |
| Everything is squashed | Use a smaller scale |
| No intersection is visible | Zoom out or recenter near the crossing |
| Only one crossing is visible | Check whether another crossing is outside the window |
GDC walkthrough
Step through the exact calculator keystrokes, screen by screen, in study mode.
IB trap: If the question asks for all solutions, do not stop after finding the first visible intersection.
Check the full relevant domain.
Get feedback like a real examiner
Submit your answers and get instant feedback — what you did well, what's missing, and exactly what to write to score full marks.
Reading and rounding calculator output
Worked example
The calculator gives the intersection point (2.381, 5.762).
Report the solution to 3 significant figures.
Step by step
- Round the x-coordinate to 3 significant figures.
- Round the y-coordinate to 3 significant figures.
- Write the coordinate pair in the correct order.
Final answer
(2.38, 5.76)
Common mistake: Do not swap the coordinates.
The calculator gives x first, then y.
When there is more than one intersection
One graph pair can have several solutions: A line and a curve can meet more than once.
Technology helps you find each intersection, but you must remember to report all relevant solutions.
Worked example
A calculator shows intersections at x = −1 and x = 3.
The question asks for all solutions.
What should you write?
Step by step
- The word all means every relevant intersection is needed.
- Write both x-values as solutions.
Final answer
x = −1 and x = 3
Do not stop too early: After finding one intersection, scan the graph or use the intersect tool again near another crossing.