(根号7+根号2)^2+(根号7-根号2)^2求过程
用a/b代替,写起来简单点,根号7=a,根号2=b
则=（a+b）^2+(a-b)^2
=a^2+b^2+2ab+a^2+b^2-2ab
=2 (a^2+ b^2)
=2(7+2)
=18