Question

How do you multiply `(sqrt10 - 9)^2` and write the product in simplest form?

Answer 1

You can write (considering that `(a-b)^2=a^2-2ab+b^2`):

`(sqrt(10)-9)*(sqrt(10)-9)=(sqrt(10))^2-2*9*sqrt(10)+9^2=`
`=10-18sqrt(10)+81=`
`=91-18sqrt(10)=`