Question

11.A cylinder has a radius of 4x + 2 and a height of 5x + 4. Which polynomial in standard form best describes the total volume of the cylinder? Use the formula V = r2h for the volume of a cylinder.
80x3 + 144x2 + 84x + 16
80x3 – 144x2 + 84x + 16
80x3 + 144x2 + 84x – 16
80x3 + 144x2 – 84x + 16

12.A sphere has a radius of 4x + 4. Which polynomial in standard form best describes the total surface area of the sphere? Use the formula S = 4r2 for the surface area of a sphere.
64x2 + 128x + 64
64x2 – 128x + 64
64x2 + 128x – 64
64x2 – 128x – 64

Answer 1

so you will have

\[V = (4x + 2)^2 \times (5x + 4)\]

all you need to do is distribute and collect like terms...

but a hint is that very term will be positive... as you will be multiplying postive terms by positive terms... so this may save a little work.

Answer 2

thx but i still have no clue

Answer 3

80x3 + 144x2 + 84x + 16 could this possibly be it?

Answer 4

ok... so in question 11... in which equation is every term positive...

Answer 5

thats it.... every term is positive.... and it saves a bit of work...

as you would have had

\[(16x^2 + 16x + 4)\times(5x + 4)\]

Answer 6

question 12

you would have

\[S = 4 \times (4x+4)^2\]

all the terms in r are positive...

so when you square positives, you get positives...

so look for the equation where every term is positive.

Answer 7

64x2 + 128x + 64?