x- and y- intercepts
At what point does the line cross the y-axis? (0,2) (0,-1) (0,2) What do you notice about all the points? They all have 0 for the x-coordinate. (0,y)
y-intercept: the point where a line crosses the y-axis
At what point does the line cross the x-axis? (2,0) (-3,0) (1,0) What do you notice about all the points? They all have 0 for the y-coordinate. (x,0)
x-intercept: the point where a line crosses the x-axis
NOTICE: On the y-intercept there is a zero as the x value. And the x-intercept has a zero as the y value.
FINDING THE X- AND Y-INTERCEPTS FROM AN EQ: TO FIND THE X-INTERCEPT: TO FIND THE Y-INTERCEPT: Plug a zero in for y. Plug a zero in for x. X-INTERCEPT: Graph Y-INTERCEPT:
NOW, LET'S GRAPH USING THE INTERCEPTS X-INTERCEPT: Y-INTERCEPT:
Find the x- and y- intercepts for: ½ x – 4y = 6 x-intercept: ½ x – 4y = 6 ½ x – 4(0) = 6 ½ x = 6 ½ ½ x = 12 (12, 0) y-intercept: ½ x – 4y = 6 ½ (0) – 4y = 6 - 4y = 6 -4 -4 y = -1.5 (0, -1.5)
What are the x- and y- intercepts for the following tables? -2 -9 -1 -6 -3 1 2 3 X Y -3 2 -2 -1 -4 1 -6 X Y -5 -2.5 -3 -1.5 2 1 4 x-intercept: x-intercept: x-intercept: (1,0) (-2,0) (0,0) y-intercept: y-intercept: y-intercept: (0,-3) (0,-4) (0,0)
TO FIND THE X-INTERCEPT: TO FIND THE Y-INTERCEPT: Plug a zero in for y. Plug a zero in for x. Now solve for y. Y-INTERCEPT: X-INTERCEPT:
Graph the lines given the x- and y- intercepts. x-intercept: 2 y-intercept: -3 x-intercept: -5 y-intercept: -2
LET'S LOOK AT A WORD PROBLEM: If it costs $2.00 to connect a call and $.25 per minute to talk. What are the x- and y- intercepts of this situation? Write the equation. What is the slope? Graph cost per minute What is the y-intercept? the connection fee
LET'S FIND THE INTERCEPTS: What does b=? So, the y-intercept is: TO FIND THE X-INTERCEPT: Plug a zero in for y. Now solve for x. X-INTERCEPT: