题目

This is __________ watch. That is __________ ID card. A . a, a B . a, an C . an, a D . an; an 答案：B（Ⅰ）若实数s，t是方程20x2+14x+1=0的两不等实根，求值：s2+t2；（Ⅱ）若实数s，t分别满足20s2+14s+1=0，t2+14t+20=0且st≠1，求值：st+4s+1t．