Question

Which is a sum of cubes? a3 + 18 a6 + 9 a9 + 16 a12 + 8

a3 + 18


a6 + 9
a9 + 16
a12  + 8

Answer 1

D. a12 + 8

Explanation:

I took the test and got it correct! :3

Answer 2

Answer:
`a^(12)+8`

Explanation:

let's check all the expressions

1.
`a^3+18`

here 18 is not a perfect cube.

2.
`a^6+9`

here 9 is not a perfect cube.

3.
`a^9+16`

here 16 is not a perfect cube.

4.
`a^(12)+8`

here 8 is a perfect cube, thus we can write above expression by using laws of exponents as

`(a^4)^3+2^3`

Thus,
`a^(12)+8` is a sum of cubes.