Answer:
The format of the equation of a line is y=mx+c so in order to know whether which line is perpendicular to line y=5x-9, gradient of y=5x-9,which is 5,has to multiply by another gradient to get -1.[in short m1×m2=-1]
So the equation perpendicular to line y=5x-9 has a gradient of -1÷5=-1/5
