题目

已知x，y满足约束条件，则的最大值是（ ） A. -1                  B. -2                  C. -5                  D. 1 答案：A 【解析】 根据题意作出约束条件确定的可行域，如下图： 令，可知在图中处，取到最大值-1,故选A. 考点：本题主要考查了简单的线性规划. When you were young, who rode you around on the back of his bike? Who played football and ______ kites with you in the park? Who helped you work out the difficult math problem? Who taught you the difference between right and wrong?Your dad. Now it is your turn to do something for ______. The third Sunday in June is Father's Day. So why______ do some things to thank your dad for all his love and support（支持）?The idea of Father's Day came from an ______ lady called Samara Smart Dodd in 1909. She wanted an unusual day to remember her ______. He raised（抚养）six children by himself ______ his wife died. Dodd thought there needed to be a day to thank all the great, selfless and loving dads. Her father was born ______, so she wanted to hold the first Father's Day celebration（庆祝）on his birthday in 1909. In 1924, most of the Americans like the idea of Father's Day. In the end, the third Sunday in June was named Father's Day.There are many ways ______ your love and thanks. Send him a postcard. Usually fathers like cards. So, maybe a good one can make him laugh. A small gift, such as a photo of your family or a lovely wallet ______ make him feel like a king. Send him flowers：the rose is the official Father's Day flower. At last don't ______ to say "I love you, dad!"【1】A.flewB.boughtC.soldD.played【2】A.youB.herC.hisD.him【3】A.don'tB.doesn'tC.notD.didn't【4】A.EnglishB.IndianC.AfricanD.American【5】A.motherB.fatherC.grandfatherD.brother【6】A.whenB.untilC.afterD.before【7】A.in MayB.in JulyC.in JuneD.in August【8】A.to giveB.to showC.to bringD.to say【9】A.shouldB.canC.mustD.need【10】A.rememberB.forgetC.to forgetD.to remember