Wize High School Grade 9 Math Textbook > Analytic Geometry: Equation of a Line

Finding the Equation of a Line
To find the equation of a line, we need at least 2 pieces of information
The slope and the y-intercept
The slope and the x-intercept
The slope and a point on the line
Two points on the line
A point on the line and the equation of the line that is parallel to it
A point on the line and the equation of the line that is perpendicular to it

Wize Tip
If the slope and y-intercept is given, it's easiest to use y=mx+by=mx+by=mx+b.

Otherwise, it's usually easiest to use y−y1=m(x−x1)y-y_1=m(x-x_1)y−y1​=m(x−x1​)!

We don't usually use the standard form Ax+By+C=0Ax+By+C=0Ax+By+C=0 when trying to find the equation of a line.

Practice: Finding Equations of Lines
Determine the equation of each line based on the information given.
a) The line that has a slope of 333 and passes through the point (0,−1)(0,-1)(0,−1).

b) The line that has a slope of −2-2−2 and passes through the point (−1,3)(-1,3)(−1,3).

c) The line that passes through the point (3,−8)(3,-8)(3,−8) and (1,−6)(1, -6)(1,−6).

a) Enter your answer in the form

y=...

b) Enter your answer in the form

y=...

c) Enter your answer in the form

y=...

I don't know

Practice: Finding Equations of Lines
Determine the equation of each line based on the information given.
a) The line that passes through the point (4,4)(4,4)(4,4) and is parallel to the line x−2y−8=0x-2y-8=0x−2y−8=0.

b) The line that passes through the point (0,0)(0,0)(0,0) and is perpendicular to the line 2x+3y−5=02x+3y-5=02x+3y−5=0.

a) Enter your answer in the form

y=...

b) Enter your answer in the form

y=...

I don't know