Two lines have equations \(y = {m_1}x + 3\) and \(y = {m_2}x - 7\). If the lines are parallel then \({m_1} = {m_2}\) and if \({m_1} = {m_2}\) then the lines are ...

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 \(y = 2x - 2\) ...

Horizontal lines run left to right, parallel to the horizon, with slope 0 and equation y = k. Vertical lines run top to bottom, perpendicular to the horizon, with undefined slope and equation x = k.