1. Unit #7 Graphing Equations of the Line Lesson #4 X and Y Intercept

2. Opening Activity Predict which of the equations below slant right and which slant left: 1. y = x + 9 2. y = x – 8 3. y = 2x + 1 4. y = 5x 5. y = -x 6. y = 4x + 2

3. The Equation of a Line The equation of any line can be written in the following form: y = mx + b m is the slope b is the y intercept x,y are the ordered pairs

4. The Equation of a Line Example y = 2x + 4 Y = mx + b Slope = 2 Y intercept 4 or (0,4)

5. X Intercept You can calculate the X intercept by using the original equation. In order for a line to cross the x axis the y coordinate would have to be 0. If y is 0 then we would put the number 0 in for y in the equation and then calculate. The answer that is calculated is the x intercept.

6. X Intercept Example y = x + 9 0 = x + 9 0 – 9 = x + 9 – 9 -9 = x Therefore the x intercept would be (-9,0)

7. Examples Give the x and y intercepts for the following equations: EquationY interceptX intercept y = x + 11 y = -x – 7 y = x + 1 y = -3x – 2 y = 3x - 4

8. Constant Functions An equation like this one, y = 5, is called a constant function. The y coordinate always stays the same. They run parallel to the x axis. They are straight lines that run through that point on the y axis, the y intercept. It has a slope of Zero. They do not have x intercepts.