The radius of a cylinder is 3x-2 cm. The height of the cylinder is x+3 cm. What is the surface area of the cylinder? The choices are:

Question

2pi(3x^2 + 10x - 8)
2pi(12x^2 + 7x - 2)
2pi(12x^2 - 2x + 13)
2pi(12x^2 - 5x - 2)

Please help me in setting this up and solving. Thanks

Answer 1

surface area = 2pi (r^2 + rh)(it is the formula)

So, we just plug it in.

ignoring the 2 pi, we see that r^2 = (3x-2)^2 = 9x^2-12x+4

r*h = (3x-2)(x+3)

Then we get for rh = 3x^2-2x+9x-6 =

3x^2 +7x-6.

We add these together to get 12x^2 -5x-2

multiply by 2pi we get

2pi(12x^2-5x-2)

That is the answer and thus it is D

Answer 2

1.A
2.D
3.B
4.D
5.C