Step-by-step explanation:
the equation is
y = ax + b
a is the slope of the line. this is the ratio y/x indicating how many units y changes, when x changes a certain number of units.
so, when we go from A to B, x changes 2 units (from 3 to 5), and y changes -4 units (from 5 to 1).
so the slope is -4/2 = -2
now or equation looks like
y = -2x + b
to get b we use one of the points in the equation. e.g. B
1 = -2×5 + b = -10 + b
b = 11
so, our full equation is
y = -2x + 11
