《玫瑰三愿》是由()作曲。A、萧友梅 B、龙七 C、聂耳 D、黄自 发布时间:2018-08-31 19:20 │ 来源:www.tikuol.com 题型:单项选择题 问题: 《玫瑰三愿》是由()作曲。A、萧友梅B、龙七C、聂耳D、黄自
题型:单项选择题 先阅读下面材料,然后解答问题:王老师在黑板上出了这样一道习题:设方程2x2-5x+k=0的两个实数根是x1,x2,请你选取一个适当的k值,求x2x1+x1x2的值.小明同学取k=4,则方程是2x2-5x+4=0.由根与系数的关系,得x1+x2=52,x1x2=2.∴x2x1+x1x2=x22+x12x1x2=(x1+x2)2-2x1x2x1x2=254-2×22=98即x2x1+x1x2=98.问题(1):请你对小明解答的正误作出判断,并说明理由.问题(2):请你另取一个适当的正整数k,其它条件不变,不解方程,改求|x1-x2|的值. 查看答案
题型:单项选择题 Though ______ money, his parents managed to send him to university. [ ]A. lackedB. lacking ofC. lacking D. lacked in 查看答案
题型:单项选择题 —It’s noisy.—The office upstairs ______ , which _______ two weeksA.will decorate , will lastB.will be decorated , will be lastedC.is being decorated, will lastD.is decorating .is lasting 查看答案