"find the equation of the line passing through B, with positiion vector b, which is perpendicular to the line r=a + c, c=/=0, given that B is not a point on the line". hi, i dont even get this at all to be honest, how is r=a + c a line? in terms of normal line equations, which is the gradient, and the intercept? because r and c are not axis they are vectors, i dont know what this is asking.