G'day, kimbero5!
First we use the straight line equation:
y - y1 = m(x - x1)
where (x1,y1) is any point on the line, and where m is the gradient.
We have a point (1,-2) and a gradient of 2.
Plugging into the equation as above:
y - (-2) = 2(x-1)
Expanding the brackets
y + 2 = 2x - 2
Bring the 2 and the y from the left hand side to the right hand side by subtracting gives:
0 = 2x - y - 4
Or
2x - y - 4 = 0
This is a standard form (ie. having it equal to zero). The other common form being y=mx + c. If you want a "C" on the right hand side as you have said then here you would have 2x - y = 4.
