Slope of a straight line!!!

Slope of a line is defined as the ratio of y coordinate difference to x coordinate difference.
For eg. the slope of a line (m) passing through points (x1, y1) and (x2,y2) is m = (y2-y1)/(x2-x1).

Slope of a line perpendicular another line would be the negative reciprocal slope.
ie, slope of line perpendicular (m2) to a line having slope m is

m2 = -(1/m)

The general equation of a line is y-y1 = m(x -x1) + c where c is the y intercept and passing through (x1,y1) having slope m.

You can find the equation of a line perpendicular to this line as well by finding slope of this line.
You cam have more info on this at http://mathforum.org/library/drmath/view/66642.html

Visit http://www.analyzemath.com/EllipseEq/EllipseEq.html for applet to explore the properties of circle, ellipse, parabola and hyperbola