Question 667805
Step 1: Find the slope of the line that passes through those two lines. 

{{{m = (y2-y1)/(x2-x1) = (1-(-3))/(2-(-1)) = (1+3)/(2+1) = 4/3}}}

Step 2: Put into point slope form. Choose either point. We'll choose (2,1).

{{{(y-y1) = m(x-x1)}}}
{{{(y-1) = (4/3)(x-2)}}}
{{{y-1 = (4/3)x - 8/3}}}
Since we know we're going into standard form Ax+Bx=C where A,B are integers, we know we cannot have fractional coefficients of x or y. (Since fractions are rational not integers) So, to make life easy, let's multiply the entire equation by 3 to get rid of the fractions.

{{{3(y-1) = 3((4/3)x-8/3))}}}
{{{3(y-1) = 4x-8}}}
{{{3y-3 = 4x -8}}}

{{{-4x + 3y = -5}}}