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Graph of Linear Equations

# Equations of straight lines

When working with straight lines, there are often many ways to arrive at an equation. Let's see:

Slope Intercept Form
(if you know the slope and where the
line crosses the y-axis, use this form)

y = mx + b

m = slope
b = y-intercept
(where line crosses the y-axis.)

Point Slope Form
(if you know a point and the slope,
use this form)

m = slope
= any point on the line.

and...

Find the equation of the line that goes through two points P(x 1,x2) and Q(y1,y2)
Firts find the slope using $m=\frac{y_2-y_1}{x_2-x_1}$
and then use the formula:

Write the slope-intercept form of the equation of the line with the slope 2 that contains the point (-4,-5).
Use the slope-intercept form to find b:
y=mx+b
-5=2·(-4)+b
8-5=b
3=b

Then y=2x+3

 Write the equation of the line that contains point P(7,-8) and has slope m= -2 Solution: y= x+