To determine the behavior of the graph, we calculate the slope-intercept form of the graph. It is given by
y = mx + b
Here, b is the y-intercept.
m is the slope of the graph that is the difference between y-axis over x-axis.
m = (y2 - y1) / (x2 - x1)
To calculate both points, let's pick two points from the graph.
For example, the first point is (1, 250) and the second point is (2, 200)
So,
(x1, y1) = (1, 250)
x1 = 1
y1 = 250
(x2, y2) = (2, 200)
x2 = 2
y2 = 200
Now, put these values in slope form, we get
m = (200 - 250) / (2 - 1)
m = -50
Hence, the slope is -50 that tells that with every on increase in the value of x, y is decreasing 50. Hence, if I decrease the value of x, y will rise 50.
Therefore,
I can say that when x = 0, y = 300. (0, 300)
Therefore, b = 300
Now, put all these values in the slope-intercept form.
y = mx + b
dt = -50x + 300
Hence, the 3rd option is correct.