Simply plug your y intercept in for b. You’ll get y= -3x+4. Draw a simple graph and plot your y coordinate first at 4. Since your slope is -3, then from your point 4 on the graph go down 3 spaces and to the right 1 space. Continue on until you get a line. Also, from 4, go up 3 spaces and to the left 1 space to complete the line.
