解答
(1)√32-3√18+6√2
(2)(2√7-3√5) (√7+√5)
(1) √32-3√18+6√2 = √42×2-3√32×2+6√2 = 4√2-3×3√√2 +6√√2
= 4√√2-9√√2+6√2 = (4-9+6)√2=√√2
(2)(2√7-3√5)(√7+√5)
=
=2√7×√7+2√√7 × √5-3√√5 × √7-3√√5 × √√5
==
= 2x7+2√35 - 3√35-3 × 5
= 14-√35-15=-1-√√35
(a+b)(c+d)= ac+ad +