If DF=9x-39, find EF

Answer 1

Since we don't know where E is in relation to D or F, we don't know if the lines are perpendicular or not. If it was, the lines being perpendicular would mean that the slope would have to be the negative reciprocal of 9 or -1/9x. With that slope, we can use point slope form to find the line that contains EF-(-39)=-1/9(x-0). Simplifying that would give EF+39=-1/9x or the line that contains EF is y=-1/9x-39.