Can someone check what I did wrong when solving (a+sqrtb)^3+(a+-sqrtb)^3?

Question

anonymous · Answer

attachment

anonymous · Answer

The circled equations are the two things I am adding together

hartnn · Answer

the very first step

whats the square of $\sqrt b$
 ?

anonymous · Answer

Ohhhh, its b.

hartnn · Answer

yes

anonymous · Answer

in the second line from the top, how'd you get
$$a ^{2}+a \sqrt{b}+b^2$$?

anonymous · Answer

Writing error. Thanks!

anonymous · Answer

isn't there a 2 in front of the $$a \sqrt{b}$$?

hartnn · Answer

let us know if you don't get 
$ 2a (a^2 + 3b) $
in the end, after the correction :)

hartnn · Answer

there should be a 2 also, 
as correctly pointed out by @jaeuni

anonymous · Answer

So (a+b)^3 is different from a^3+b^3 right?

anonymous · Answer

yes (a+b)^3 means that 
(a+b)(a+b)(a+b)

anonymous · Answer

Alright, thank you so much for your help!

anonymous · Answer

np make sure to add the 2's for both the ( ) since that'll also change up your work as well