If x and y satisfy x2 + y2 = 1, then the minimum value of (Y-2) / (x-1) is; the maximum value of X / 3 + Y / 4 is I don't understand why (Y-2) / (x-1) can be regarded as the slope of the line between any point (x, y) and point (1,2) on a circle

If x and y satisfy x2 + y2 = 1, then the minimum value of (Y-2) / (x-1) is; the maximum value of X / 3 + Y / 4 is I don't understand why (Y-2) / (x-1) can be regarded as the slope of the line between any point (x, y) and point (1,2) on a circle

Defined by the slope, the slope of the line between point (x, y) and point (1,2) = (Y-2) / (x-1),
x. Y satisfies x ^ 2 + y ^ 2 = 1,
The point (x, y) is on the circle x ^ 2 + y ^ 2 = 1