a-b=4,ab=1所以a²+b²=(a-b)²+2ab=16+2=18（1）a4次方+b4次方 = (a²+b²)² - 2(ab)² = 18² - 2 = 322（2）b/a+a/b = (a²+b²)/ab = 18 / 1 = 18这种题考的就是(a+b)...