Intermediate Algebra/Linear Equations

Linear EquationsEdit

A linear equation is an equation that forms a line on a graph.

Slope-Intercept formEdit

A linear equation in slope-intercept form is one in the form   such that   is the slope, and   is the y-intercept. An example of such an equation is:

Finding y-intercept, given slope and a pointEdit

The y-intercept of an equation is the point at which the line produced touches the y-axis, or the point where   This can be very useful. If we know the slope, and a point which the line passes through, we can find the y-intercept. Consider:

  Which passes through  
  Substitute   and   for   and  , respectively
  Put into slope-intercept form.

Finding slope, given y-intercept and a pointEdit

The slope of a line is defined as the amount of change in x and y between two points on the line.

If we know the y-intercept of the line, and a point on the line, we can easily find the slope. Consider:

  which passes through the point  
  Replace   and   with   and  , respectively.   Simplify.     Put into slope-intercept form.

Standard formEdit

The Standard form of a line is the form of a linear equation in the form of   such that   and   are integers, and  .

Converting from slope-intercept form to standard formEdit

Slope-intercept equations can easily be changed to standard form. Consider the equation:
  Subtract -3x from each side, satisfying  
  Multiply the entire equation by  , satisfying  
  and   are already integers, so we don't have to worry about changing them.

Finding the slope of an equation in standard formEdit

In the standard form of an equation, the slope is always equal to