Line y = kx + b passes through points A (0; 2) and B (3; -1). Write the equation of this line.

If the straight line y = kx + b passes through the point O (x1; y1), then the following relation is true:
y1 = kx1 + b.
According to the condition of the problem, the straight line y = kx + b passes through the point A (0; 2), therefore, the following relation is true:
2 = k * 0 + b.
It is also known that this line passes through the point B (3; -1), therefore, the following relation is true:
-1 = k * 3 + b.
We solve the resulting system of equations.
From the first equation it follows that b = 2. Substituting this value b into the second equation, we get:
-1 = k * 3 + 2.
We solve the resulting equation:
k * 3 = -1 – 2;
k * 3 = -3;
k = -3/3;
k = -1.

Answer: the straight line y = -x + 2 passes through the points A (0; 2) and B (3; -1).