We define the following variables:
• t(x) = thickness of the ice in terms of x,
,• x = days since the discovery.
From the statement of the problem we know that:
• the thickness on the day of the discovery (x = 0) was t = 625,
,• the thickness is decreasing at an average rate of 0.72 m per day.
Because the thickness is decreasing the same thickness each day, the problem can be described by a linear function:
[tex]t(x)=m\cdot x+b,[/tex]where:
• b is the value of t when x = 0, i.e b = 625,
,• and m is the rate of change of the thickness, m = -0.72.
Replacing the values of m and b in the equation above we get:
[tex]t(x)=-0.72x+625=625-0.72x\text{.}[/tex]Answer
B: t(x)=625-0.72x
