Any equation that can be rearranged into the form \(y = mx + c\), will have a straight line graph. \(m\) is the gradient, or steepness of the graph, and \(c\) is the \(y\)-intercept, or where the line ...
Parallel lines are a fixed distance apart and will never meet, no matter how long they are extended. Lines that are parallel have the same gradient. The graphs above, \(y = 2x + 1\) and \(y = 2x - 2\) ...