Question

How do you multiply `(5 + 3sqrt7) (-4+5rsqrt7)`?

Answer 1

`color(indigo)(=> 5r (5 sqrt7 + 21) - 4(5 + 3 sqrt7)`

Explanation:

`(5+3 sqrt7) (-4+ 5r sqrt7)`

`=> -20 - 12 sqrt7 + 25 r sqrt7 + 15 r *7`, removing brackets and multiplying terms

`=> -20 - 12 sqrt7 + 25 sqrt7 r + 105r`

`color(indigo)(=> 5r (5 sqrt7 + 21) - 4(5 + 3 sqrt7)`