y=4x+9 Start with the given equation
1y-4x=4x+9-4x Subtract 4x from both sides
-4x+1y=9 Simplify
-1*(-4x+1y)= -1 *(9) Multiply both sides by -1 to make the A coefficient positive (note: this step may be optional; it will depend on your teacher and/or textbook)
4x-1y=-9 Distribute and simplify
The original equation y=4x+9 (slope-intercept form) is equivalent to 4x-1y=-9 (standard form where A > 0)
The equation 4x-1y=-9 is in the form Ax+By=C where A=4, B=-1 and C=-9
