Answer:

Step-by-step explanation:
Hi!
Lets call:
T = temprature of the object
T₀ = temperature of surroundings
t = time
The rate of change of T is its derivative with respecto to time. If T > T₀, the object looses heat, so T decreases. Then, being k > 0:

In this case T₀ = 70ºF and k = 0.05/min. Then the differential equation is:

Answer:
Midpoint formula.
The midpoint formula is (x_1+x_2)/2 , (y_1+y_2)/2
Step-by-step explanation:
This is one method. A list wasn't provided.
Let
The origin of coordinates the tree
r1 = vector position of the child 1.
r2 = vector position of the child 2
Child 1:
r1 = (12i + 12j)
Child 2:
r2 = (-18i + 11j)
The scalar product will be given by:
r1.r2 = ((12) * (- 18)) + ((12) * (11)) = - 84
The scalar product of their net displacements from the tree is -84m ^ 2