Find the equation of the straight line that passes through the points (−1, 5) and (5, −1). Find the coordinates of the point where this line crosses the y-axis.

The slope is [5 - (-1)]/(-1 -5) = -1

The equation is y = -x + b

To pass through (-1,5),
5 = 1 + b
b = 4

y = -x +4

The y-intercept is at (0,4) .