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Intercepts: Graphing Using Intercepts
STOP!
Y
Ex: Graph X + 2y = 4
Step 1: Set Y = 0 and solve for X
x=2 (0)=4
x=2(0) =4
x=4
Step 2: Set X=0 and solve for Y
0 + 2y = 4
0 + 2y = 4
2 2
y=2
Step: 3: Put a point on X-axis at x = 4 and a point on Y-axis at y=2
Interval to Plus Minus Notation
= 4.9
STOP!
Convert ( 3.2, 6.6 ) + +/- notation
Step 1: Find the middle of the interval by adding the endpoint and dividing by 2
6.6 + 3.2
2
Step 2: Find the distance from the middle to the endpoint
6.6 - 4.9 = 1.7
Step 3: In +/- notation
4.9 +/- 1.7
Plotting Points
Ex. Plot (2,3) = (x,y)
X tells you how far to go right or left
Y tells you how far to go up or down
So, for (2,3), start from the origin. I'm going:
2 units right because x=2
3 units up because y=3
Ex: Plot ( -1, -4)
This time, Because X = -1 I'm moving 1 unit left
and because Y = -4, I'm moving 4 units down
Y
Y
3 up, y=3
2 right, x=2
(2,3)
(-1,-4)
Graph Through Origin and Slope
Ex: Graph Y = 3x
Step 1: Set X=0, Solve for Y
Y=3(0)
Y=0
(0,0)
Step 2: Set X=1, Solve for Y
Y=3(1)
Y=3
(1,3)
Step 3: Plot the points. Join with a line.
Y
Ex: Y=1x or X
4
4
Y
Calculate Slope
Ex: Find slop of the line joining (3,-1) and (5,6)
b= y2 - y1
x2 - x1
Step 1: Identify the given points, as (X1,Y1) and (X2 Y2)
(31 - 1) (5,6)
X1 Y1 X2 Y2
Step 2: Write slop formula, plugging in the values
b= y2 - y1
x2 - x1
=
=
3.5 or 7/2
6 - (-1)
5 - 3
Use calculator: Shown in video
6 - (-1)
5 - 3
Step 1: Set X=0, Solve for Y
Y=1/4 (0)
Y=0
(0,0)
Step 2: Set X=4 (the denominator of the fraction)
Y=1/4 (4)
Y=1/4 (4)
Y=1
(4,1)
Step 3: Plot the point. Draw the line.