hi i'm struggling with this:
when a parabola crosses the x-axis at the points A and B, the axis of symmetry is the perpendicular bisector of the line joining the points A and B. since A is the point (-5, 0) and B is the point (2/3, 0) the equation of the line of symmetry is x = -13/6
i know that the mid point is -13/6 but why is that the equation? i thought you had to go through the whole y - y1 = m(x - x1) business. when the gradient of a horizontal line is 0 how do you come to the conclusion that the equation is x = -13/6.
thanks for any help
i'm sorry but i don't really understand what you mean, i literally took up maths about 2 weeks ago. what would the equation of the horizontal line be and how would you figure that out? to find the perpendicular bisector i know you need to reverse the gradient around ie m1 * m2 = -1 but i can't see how you'd do anything when the gradient is 0. why do you not use the y - y1 = m(x - x1) can you explain in detail please how and why its all done?