a) Find the equation of the line passing through the points $(1,-2)$ and $(3,-10)$

Step 1 ：Given two points (1,-2) and (3,-10), we can find the equation of the line passing through these points.

Step 2 ：First, we calculate the slope (m) of the line using the formula (y2 - y1) / (x2 - x1). Substituting the given points into the formula, we get m = (-10 - (-2)) / (3 - 1) = -4.

Step 3 ：Next, we use the point-slope form of a line, which is y - y1 = m(x - x1), where m is the slope and (x1, y1) is a point on the line. We can use either of the given points for (x1, y1). Let's use the point (1,-2). Substituting these values into the formula, we get y - (-2) = -4(x - 1).

Step 4 ：Simplifying the equation, we get y = -4x + 2.

Step 5 ：Final Answer: The equation of the line passing through the points (1,-2) and (3,-10) is \( \boxed{y = -4x + 2} \).