Summary: Equations of Lines

Key Concepts

  • Given two points, we can find the slope of a line using the slope formula.
  • We can identify the slope and [latex]y[/latex]-intercept of an equation in slope-intercept form.
  • We can find the equation of a line given the slope and a point.
  • We can also find the equation of a line given two points. Find the slope and use point-slope form.
  • The standard form of a line has no fractions.
  • Horizontal lines have a slope of zero and are defined as [latex]y=c[/latex], where c is a constant.
  • Vertical lines have an undefined slope (zero in the denominator) and are defined as [latex]x=c[/latex], where c is a constant.
  • Parallel lines have the same slope and different [latex]y[/latex]intercepts.
  • Perpendicular lines have slopes that are negative reciprocals of each other unless one is horizontal and the other is vertical.

Glossary

slope
the change in [latex]y[/latex]values over the change in [latex]x[/latex]–values