The length of a rectangle is 7 cm, and the width is 4cm, If both the length and the width are increased by equal amounts, the area of the rectangle is increased by 42cm^2. How do I find the length and width of the larger rectangle? How can I show that the points [math]P (2,-3), Q(3,1)[/math] and [math]R(5,9)[/math] are collinear?