Stage: 3 Challenge Level: 
It may help to keep one variable fixed and just change the other one:
you could keep the gradient fixed and change the intercept,
or you could keep the intercept fixed and change the gradient.
How do these changes affect the equation of the line?
Maths in STEM. Linear functions. Graphs. Speed. Parallel lines. Tangent. Length/distance. Cartesian equations of lines. Gradients. Quadratic functions.
Published July 2007,August 2007,July 2009,August 2009.
Copyright © 2007. University of Cambridge. All rights reserved.
NRICH is part of the family of activities in the Millennium Mathematics Project, which also includes the Plus and Motivate sites.
email: nrich@damtp.cam.ac.uk