How do you write the equation of a strait line by just looking at it on the graph?

Answer 1

Slope intercept form:

y = mx + b

Where m is the slope (rise/run)

Example: A line going up at a 45 degree angle has a slope of 1

Goes up 1, over 1 to get to the next point on the line.

1/1 = 1

And b is the y-intercept (Where the line crosses the y axis)

Answer 2

There are two parts to the equation: the constant part and the variable part. In other words,

y = M x + B

This is called "Slope-intercept" form. The constant part ("B" above, the "intercept" part) is where the line intersects the X axis. First look at the place where it intersects the X axis, then you make B equal to the place where it intersects.

The variable part ("M" above, the "slope part") is figured by figuring out the rise/run of the line. Look at the graph: how many units does the line move UP (rise) for every unit it moves SIDEWAYS (run)? That's the slope, and it's what you set "M" in the above equation to. If the line rises 2 units for every unit it moves to the right, the slope is 2.

Here's an example, that tells you more about calculating the slope:

http://www.purplemath.com/modules/slope.htm

The first example shown on that page would have B=-4, M=2/3 (it goes up 2 for every 3 it moves to the right). Therefore the equation is

y = 2/3 x - 4

Calculate some example values:

x = 6 ----> y = 0
x = 3 ----> -2
x = 12 ----> y = 4

Answer 3

y=mx+b
find the y coordinate
then the slope m
and the x coordinate and then plug those numbers in to find b.

Answer 4

use this formula: y=mx+b

b is the y-intercept, and m is the slope. easy as that.