Final answer:
To find the y-intercept of line AB, we can use the point-slope form of a linear equation. The equation of line BC is y = -2x + 4, and the x-coordinate of point C is -4.5.
Step-by-step explanation:
To find the y-intercept of line AB, we can use the point-slope form of a linear equation, which is y - y1 = m(x - x1). Given the coordinates of point B (2, 1) and the fact that BC forms a right angle, we can calculate the slope of line AB as -2. Using the coordinates of either point A or B (let's use point B), we substitute the values into the point-slope form and solve for y:
1 - y1 = -2(x - x1)
1 - 1 = -2(x - 2)
0 = -2x + 4
y = -2x + 4
Therefore, the equation of line BC is y = -2x + 4. If the y-coordinate of point C is 13, we can substitute this value into the equation and solve for x:
13 = -2x + 4
9 = -2x
x = -4.5
Therefore, the x-coordinate of point C is -4.5.