Finding the equation of a line.
First deduce the gradient through the formula Rise over Run. Then substitute the the co-ordinates of the first point to deduce the y-intercept.
To get a faster equation: Change the equation into the format (x/a + y/b = 1)
Ex. y = 1/2x - 3
1/2x + y = -3
x/-2 + y/1 = -3
x/6 + y/-3 = 1 //
However, if the the question asks for the equation in terms of y=mx+c, just do it like this:
x/6 + y/-3 = 1
-3x/6+y = -3
-1/2x + y = -3
y = 1/2x -3//
Question: When doing x/a + y/b = 1, why must it equal to 1?