The straight line y = kx + b passes through points A (3; 8) and B (-4; 1). Write the equation for this straight line.

Substitute the coordinates of points A (x = 3, y = 8) and B (x = -4, y = 1) into the equation of the line. We compose a system of equations:
8 = 3k + b
1 = -4k + b
The second equation is multiplied by -1.
8 = 3k + b
-1 = 4k-b
Now we add the equations:
8-1 = 3k + 4k
7 = 7k
k = 1
Let us express b from the first equation:
b = 8-3k
b = 8-3 * 1
b = 5
We substitute the found k and b into the equation of the straight line:
y = 1 * x + 5
Answer: y = x + 5.