Answer:
Step-by-step explanation:
This is a pretty basic related rates problem. I'm going to go through this just like I do in class when I'm teaching it to my students.
We see we have a snowball, which is a sphere. We are talking about the surface area of this sphere which has a formula of
In the problem we are given diameter, not radius. What we know about the relationship between a radius and a diameter is that
d = 2r so
Now we can have the equation in terms of diameter instead of radius. Rewriting:
which simplifies to
and a bit more to
(the 4's cancel out by division). Now that is a simple equation for which we have to find the derivative with respect to time.
Now let's look at the problem and see what we are given as far as information.
The rate at which the surface area changes is -3.8, and we are looking for 
, the rate at which the diameter is changing, when the diameter is 13. Filling in:
and solving for the rate at which the diameter is changing:
and divide to get
Obviously, the negative means that the diameter is decreasing.
Answer:
(-3.5,1)
Step-by-step explanation:
There are 7 boxes between A and B. So I figure if you take 3/4 of 7 is about 5.
30/4800 = 3/480
= 1/160 in fraction form
= 0.00625 in decimal form
<span>N(t) = 16t ; Distance north of spot at time t for the liner.
W(t) = 14(t-1); Distance west of spot at time t for the tanker.
d(t) = sqrt(N(t)^2 + W(t)^2) ; Distance between both ships at time t.
Let's create a function to express the distance north of the spot that the luxury liner is at time t. We will use the value t as representing "the number of hours since 2 p.m." Since the liner was there at exactly 2 p.m. and is traveling 16 kph, the function is
N(t) = 16t
Now let's create the same function for how far west the tanker is from the spot. Since the tanker was there at 3 p.m. (t = 1 by the definition above), the function is slightly more complicated, and is
W(t) = 14(t-1)
The distance between the 2 ships is easy. Just use the pythagorean theorem. So
d(t) = sqrt(N(t)^2 + W(t)^2)
If you want the function for d() to be expanded, just substitute the other functions, so
d(t) = sqrt((16t)^2 + (14(t-1))^2)
d(t) = sqrt(256t^2 + (14t-14)^2)
d(t) = sqrt(256t^2 + (196t^2 - 392t + 196) )
d(t) = sqrt(452t^2 - 392t + 196)</span>
Answer:
slope is -2 and the y-intercept is 12
Step-by-step explanation:
a key thing to remember: x is always equal to 0 when finding the y-intercept.
so if you look at the table for where 0 is, you get the point (0,12) meaning the y-intercept is 12.
to find the slope use the equation: slope= change in y/change in x
you can use any two points to find this.
lets take the points of the x-intercept (6,0) and the y-intercept (0,12)
12-0/0-6
12/-6
-2 = slope
