3（根号3+根号2）-2（根号3+根号5）
= 3根号3+3根号2-2根号3-2根号5
= 根号3+3根号2-2根号5
= 1.732 + 3*1.414 - 2*2.236
= 1.732 + 4.242 -4.472
≈ 1.50计算：[x+y)²-(x-y)²]÷2xy （要具体计算过程）[x+y)²-(x-y)²]÷(2xy) =[(x²+2xy+y²)-(x²-2xy+y²)]÷(2xy) = (4xy)÷(2xy) = 2