Question

(7+sqrt2)(8-3sqrt2)

Answer 1

multiply each number between the left pair of parentheses with each number between the right pair.
There are 4 multiplications:
7*8 = 56
7*-3sqrt(2) = -21sqrt(2)
sqrt(2)*8 = 8sqrt(2)
sqrt(2)*-3sqrt(2) = -3 * (sqrt(2))^2

The first answer: 56 is clear.
The second and third can be added: -13sqrt(2)
The last is -3 *2 = -6 because sqrt(2)*sqrt(2) = 2!

Now you have 56 - 13sqrt(2) - 6 = 50 - 13sqrt(2)

Hope this helps!

ZeHanz

Answer 2

Thanks!