To simplify the given expressions:

(1-√2)(3+√2)
= 13 + 1√2 - √23 - √2*√2
= 3 + √2 - 3√2 - 2
= 1 - 2√2

(√5-√18)(√5-2√2)
= √5√5 - √52√2 - √18√5 + √18*2√2
= 5 - 2√10 - 3√10 + 6√2
= 5 - 5√10 + 6√2

Therefore, the simplified expressions are:

(1-√2)*(3+√2) = 1 - 2√2(√5-√18)*(√5-2√2) = 5 - 5√10 + 6√2