One of the topics I review with almost all of the students I tutor at this time of year is the formats an equation of a line can be in. There are three formats commonly used, and they are NOT all created equal.
Today, I’m going to overview the three formats quickly, then give you the link to the much prettier handout I’ve made.
Equations of a Line
Slope-Intercept Format: y=mx+b
- m is the slope (think m for mountain)
- b is the y-intercept
- (0,b) is a good point to start graphing the line
- This is the MOST useful format
Standard Form: ax+by=c
- a and b must be integers (not fractions or decimals)
- a must be positive
- turn it into slope-intercept by subtracting ax from both sides, then dividing everything by b
Point-Slope Form: (y-y1)=m(x-x1)
- m is the slope
- x1 and y1 are coordinates for a given point
- Use point-slope for problems like this:
- Given the line 2x – 3y = 9 and the point (4, –1), find lines through the point that are:
- (a) parallel to the given line a
- (b) perpendicular to it.
You can get the PDF of the short, sweet, informative handout I made by clicking on the link below.