Question

simplify (3a-4b^3)^3 Can anyone help me? Should it be 27a^3-64b^9?
Mathway has some crazy answer...

Answer 1

no
it is
27a^3 - 72a^2b^3 - 96ab^6 + 64b^9

Answer 2

how did you get the middle part? i don't get it.

Answer 3

did you use foil and do the equation times itself then foil again for the 3rd time?

Answer 4

cubic expansion is
a^3 + a^2b + b^2a + b^3 for ( a + b ) ^ 3
its different from squaring

Answer 5

ok- thanks.

Answer 6

what you have as the "should be " answer

Answer 7

is the expansion of ( 3a)^3 - (4b^3)^3

Answer 8

is that correct though? if i was just asked to simplify?

Answer 9

= (3a - 4b^3)( 9a^2 +12ab^3 + 16b^6)

Answer 10

ahh ignore what I wrote above lol , I thought you meant that was the answer the textbook had

Answer 11

no, that was my answer. i see- so it is wrong.

Answer 12

well, I am guessing they said expand and simplify, because something factor is alot more simple than a messy cubic expansion

Answer 13

it is just a post i have to answer...simplify and then the equation.

Answer 14

i will write what i thought- seems a lot simpler than your way :)