Recall

1
Recall 1

• Slope-intercept form of the equation
• y mx b
• m is slope and b is the y-intercept.

2
Recall 1

• y mx b
• y 3x 2
• 3 is slope and 2 is the y-intercept.

3
Y 3x 2
Slope 3/1
Y
y-intercept
X
4
Recall 2

• Slope Formula
• m y2 - y1 x2 - x1

5
Recall 2

• (1, 4) and (2, 3)
• (x1, y1) (x2, y2)
• m 3 - 4 2 - 1

• Slope Formula
• m y2 - y1 x2 - x1

6
Recall 2

• m 3 - 4 2 - 1
• m -1 1

m -1
7
Write a linear Equation

• If f(2) 5 and f(6) 3
• f(2) 5 when x 2 y 5 (2,5)
• f(6) 3 when x 6 y 3 (6,3)

8
(2,5) (6,3)
When x 2, f(x) 5
f(x)
When x 6, f(x) 3
X
9
Step1 find the slope

• (2, 5) and (6, 3)
• (x1, y1) (x2, y2)
• m 3 - 5 6 - 2

• Slope Formula
• m y2 - y1 x2 - x1

10
Step1 find the slope

• m 3 - 5 6 - 2
• m -2 4

m -1/2
11
Step 2 y mx b

• y mx b
• (2,5) and (6,3)
• 5 -1/2(2) b
• 5 -1 b
• 6 b

12
Finish

• If m -1/2 and b 6, then
• y -1/2x 6 is the equation of the line.

13
Y -1/2x 6
f(x)
X
14
Your Turn

• Write an equation of the line for f(2) -2 and
  f(-4) 1
• Step 1 find the slope
• Step 2 use y mx b to find the b value.

15
Step 1 find the slope

• f(2) -2 and f(-4) 1
• (2, -2) and (-4, 1)
• Slope y2 - y1 x2 - x1

16
Step 1 find the slope

• (2, -2) and (-4, 1)
• Slope 1 - -2 -4 - 2
• Slope 3 -6

m -1/2
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Step 2 y mx b

• y mx b
• (2,-2) and (-4,1)
• -2 -1/2(2) b
• -2 -1 b
• -1 b

18
Finish

• If m -1/2 b -1, then
• y -1/2x -1 is the equation of the line.