Calculate the equation for the line: y = mx + b
First, find the slope. Find two points, and use point-slope formula:
m = slope = (y₂ - y₁)/(x₂ - x₁)
Let (x₁ , y₁) = (0 , 0) & (x₂ , y₂) = (9, 6)
slope = (9 - 0)/(6 - 0) = 9/6
Plug in 9/6 (or a simplified version) for m
y = (3/2)x + b
Now, solve for b. Get a coordinate point to use in the equation. In this case, use (6, 4), in which x = 6, y = 4
4 = (3/2)(6) + b
Simplify.
4 = (3 x 6)/2 + b
4 = 3 x 3 + b
4 = 9 + b
Isolate the b. Note the equal sign, what you do to one side, you do to the other. Subtract 9 from both sides
4 (-9) = 9 (-9) + b
b = 4 - 9
b = -5
Plug in -5 for b
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y = (3/2)x - 5 is your equation (2.); 3/2 is your slope (1.)
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