The line passing through (-4, -2) and (2, -3) is perpendicular to the line passing through (a, 5) and (2, -1). Find a.

Without using the distance formula, show that the points A(4, -2), B(-4, 4) and C(10, 6) are the vertices of a right-angled triangle.

The slope of the line which is perpendicular to the line segment joining the points (8, -5) and (-4, 7) is :

1. -1

2. 1

3. 45°

4. -45°