A is the answer because the number 8 is a constant. and the multiplication sign is the operator.
1. Each term in this polynomial has a common factor of 
:
2. Not sure what the "vertical method" is, but I would guess it refers to some way of visualizing the distributive property.
3. You can use the same approach as in (2), or recall that 
:
4. Recall that a difference of squares can be factored as 
. So
3x+17=2x+23
5x=40
40/5=8
x=8
Answer: dr/dt = 9/(24pi) cm per minute
9/(24pi) is approximately equal to 0.119366
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Work Shown:
Given info
dS/dt = 18 cm^2/min is the rate of change of the surface area
r = 6 cm is the radius, from the fact that the diameter is 12 cm
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Use the surface area equation given, apply the derivative, plug in the given values and then isolate dr/dt which represents the rate of change for the radius
S = 4*pi*r^2
dS/dt = 2*4*pi*r*dr/dt
dS/dt = 8*pi*r*dr/dt
18 = 8*pi*6*dr/dt
18 = 48*pi*dr/dt
48pi*dr/dt = 18
dr/dt = 18/(48pi)
dr/dt = (9*2)/(24*2pi)
dr/dt = 9/(24pi)
The units are cm per minute, which can be written as cm/min.
