Question

How do you multiply `(5+2sqrt6)(2+sqrt6)`?

Answer 1

In general
`(a+b)*(c+d) = (a+b)c + (a+b)d`

So we can re-write
`(5+2sqrt(6))(2+sqrt(6))`
as
`(5+2sqrt(6))(2) + (5+sqrt(6))(sqrt(6))`

`= (10 + 4sqrt(6)) + (5sqrt(6) + 6)`

`= 16 + 9sqrt(6)`