Chapter 7.6 Finding an Equation of a Line

By: Catherine Zhang Period 1

Slope-Intercept and Point-slope

Slope-Intercept

y=mx+b b=y-intercept m=slope

Point Slope

y- y₁=m(x-x₁)

Example: (5, -1), x-3y=6, Same y-intercept

Slope-intercept• (Make it a y=mx+b equation)o x-3y=6 • Subtract xo -3y=6-x • Divide by -3o y=1/3x-2 ( y=mx-2)• Plug ino -1=m(5)-2• Multiplyo -1=5m -2• Add 2 to both sideso 1=5m• Divide by 5o m=1/5 y=⅕x-2

(page 332, number 29) Textbook

Example: same slope as 2x=3y-1, (8,-5)

Slope Intercepto 2x=3y-1• Addo 2x+1=3y• Divideo y=⅔x+⅓ ( y=⅔x+b)

o -5=⅔(8)+b• Simplifyo -5=16/3+b• Subtracto -31/3=b y=⅔x-31/3

(Page 332, Number 31)Textbook

Example (5, -1), x-3y=6, SAME y-intercept

Point Slope • x-3y=6o Subtract x• -3y=6-x o Divide by -3• y=1/3x-2 ( y=mx-2)o Plug in variables• -1=m(5)-2o Simplify• -1=5m-2o Add• 1=5mo Divide• m=1/5

• y-y₁=m(x-x₁)o Plug in• y-(-1)=1/5(x-5)o Simplify• y+1=⅕x-1o Subtract y=⅕x-2

(Page 332, Number 29)Textbook

Example: Same slope as 2x=3y-1(8,-5)

o Point Intercept• 2x=3y-1o Add• 2x+1=3yo Divide• y=⅔x+⅓

( y=⅔x+b)

• y-y₁=m(x-x₁)o Plug in• y-(-5)=⅔(x-8)o Simplify• y+5=⅔x-16/3o Subtract 5 on both sides y=⅔x-31/3

(Page 332, Number 31)Textbook

THE END