#49
Top 50 Mistake
Joining plotted points with straight lines
"The Connect-the-Dots"
The Mistake in Action
Student plots points for $y = x^2$ correctly at $(-2, 4), (-1, 1), (0, 0), (1, 1), (2, 4)$ but joins them with straight line segments.
Why It Happens
Students are used to joining points with rulers and forget that curved functions require smooth curves.
The Fix
For non-linear functions, always draw a smooth curve through the points.
- Use a steady hand or a flexicurve
- The curve should have no sudden corners or kinks
- The curve should pass through or very close to all plotted points
Quick check: Does your graph have the right shape?
- Quadratic: U or ∩
- Cubic: S-shape
- Reciprocal: Two separate curves
Spot the Mistake
Can you identify where this student went wrong?
Points plotted correctly
joined with straight lines
Click on the line that contains the error.
Related Topics
Learn more about the underlying maths: