Final answer:
The equation of the line joining points (1,9) and (3,1) is y = -4x + 13
Step-by-step explanation:
The equation of a line can be determined using the formula y = mx + b, where m is the slope of the line and b is the y-intercept. Given the points (1,9) and (3,1), we can find the slope by using the formula: m = (y2 - y1) / (x2 - x1). Substituting the values (1,9) and (3,1) gives us m = (1 - 9) / (3 - 1) = -8 / 2 = -4.
Next, we can find the y-intercept by substituting the values (1,9) and the slope (-4) into the equation y = mx + b and solving for b. 9 = -4(1) + b. Solving this equation gives us b = 13.
Therefore, the equation of the line joining the points (1,9) and (3,1) is y = -4x + 13.