Hi drv123, welcome to MHF.

When the straight line is in the fourth quadrant, intercepts on the x and y axis will be either x1 and y1 or -x1 and -y1. And the angle made by the line with x -axis is obtuse. So the slope is negative. One point on the x-axis will be either (x1,0) or (-x1,0)

Then the equations of line will be

y = -(y1/x1)*(x-x1) or

y = -(y1/x1)*(x+x1)