P1 (x1, Y1) P2 (X2, Y2) are two points on a straight line with a slope of K Prove that ip1p2i = 1 + k * 2 times ix1-x2i = 1 + k * 2 times (x1 + x2) - 4x1x2 I is the vertical line, ip1p2i is the absolute value of p1p2, and ix1-x2i is the absolute value of x1-x2

P1 (x1, Y1) P2 (X2, Y2) are two points on a straight line with a slope of K Prove that ip1p2i = 1 + k * 2 times ix1-x2i = 1 + k * 2 times (x1 + x2) - 4x1x2 I is the vertical line, ip1p2i is the absolute value of p1p2, and ix1-x2i is the absolute value of x1-x2

There is a definition of slope: k = (y1-y2) / (x1-x2), so y1-y2 = K (x1-x2) | p1p2 | = under root [(x1-x2) ^ 2 + (y1-y2) ^ 2] = under root {(x1-x2) ^ 2 + [K (x1-x2)] ^ 2} = under root [(1 + K ^ 2) (x1-x2) ^ 2] = under root (1 + K ^ 2) * | x1-x2 | = under root (1 + K ^ 2) * under root [(x1 + x2) ^ 2-4 * X1 *