<span>The slope-intercept form is y=mx+b y = m x + b , where m m is the slope and b b is the y-intercept.</span>
Instantaneous rate of change = S'(r) = 8πr
S'(8) = 8π(8) = 64π
Therefore, the instantaneoud rate of change of the <span>surface area with respect to the radius r at r = 8</span> is 64π
The problem says that <span>Brandon sights a helicopter above a building that is 200 feet away at an angle of elevation of 30 degrees. So, you can calculate the height asked, by following this procedure:
</span>
Tan(α)=Opposite leg/Adjacent leg
α=30°
Opposite leg=x
Adjacent leg=200 feet
When you substitute these values into the formula above (Tan(α)=Opposite leg/Adjacent leg), you have:
Tan(α)=Opposite leg/Adjacent leg
Tan(30°)=x/200
You must clear "x":
x=200xTan(30°)
Therefore, the value of "x" is:
x=115 feet
<span>
How high above the ground the is the helicopter?
The answer is: 115 feet</span>

Actually Welcome to the Concept of the Similarities.
Since here, first figure is a Triangle, hence similarity of a triangle is given by ratio of it sides and make them equate,
hence for,
1.) 16/12 = x/9 ===> 4/3 = x/9 ===> x = 9*4/3 ==> x = 36/3
hence the value of x is 12 , ===> x = 12 .
2.) here,in the case of a Reactangle the relation is such that, length = 2* breadth,
hence we apply the relation,
x = 2*4.5 ===> x = 9 units.