Point: (2, 1), Vector: (−2, 1)
Find the equation of the line which passes through the given point and is parallel to the given vector.
Let's let the equation of the line be expressed in the form y = mx + b, where m is the slope of the line and b is the y-intercept. 

First, we can find the slope by observing that the slope of the line parallel to the vector (−2,1) is the ratio of the y-component to the x-component of the vector. This gives us a slope of 1/(-2) = -1/2. 

Now, we can use the point-slope form of the line equation: y - y1 = m(x - x1), where (x1, y1) is the given point (2,1).
Substituting the values, we get: y - 1 = -1/2(x - 2).

Finally, we can put this equation into slope intercept form by distributin -1/2 and solving for y:
y - 1 = -1/2(x - 2)
y - 1 = -1/2 x + 1
y = -1/2 x + 2

Thus, the equation of the line that passes through the point (2,1) and is parallel to the vector (−2,1) is y = -1/2 x + 2.