题目

已知关于x的一元二次方程x2+4x+m+4=0的实数根是x1，x2． （1）求m的取值范围． 当x1+x2﹣x1x2＜﹣6，且m为整数时，求m的值． 答案：解：（1）∵方程有实数根， ∴△≥0， ∴△=42﹣4×1×（m+4）=﹣4m≥0， ∴m≤0， ∴m的取值范围为m≤0； 由根与系数的关系得：x1+x2=﹣4，x1x2=m+4， ∵x1+x2﹣x1x2＜﹣6， ∴﹣4﹣m﹣4＜﹣6， ∴m＞﹣2，由（1）知m≤0， ∵m为整数， ∴m=﹣1或0． On the Labor Day, I went back to my hometown in Hunan Province with my parents. We visited our relatives, enjoyed natural view and tasted many kinds of delicious food that can only be found in the countryside. However, the most exciting thing was catching fish.That was a wonderful afternoon. The weather was pleasant and the wind was soft.After having a big meal, my uncle and my two cousins decided to catch some fish for lunch the next day. They invited me to join them and see how they catch fish to earn money. They put on special coats and boots, and then headed to the pond. The bottom of the pond was filled with thick mud, so I thought it was difficult to catch fish there.My uncle and my cousins jumped into the pond. The pond had a special drainage(排水) system so they could lead some water into another place, which made it easier to catch fish. After a while, the water level dropped and big fishes appeared. I was so amazed to see that the fishes here were two times bigger than regular ones. Out of breath, the fishes couldn't do anything but kept jumping. A great amount of mud splashed out(溅出) from the pond onto our clothes. My uncle and my cousins caught some fish skillfully. The basket was full of fishes two hours later, and they were then sent to the market.I will never forget this interesting and pleasant afternoon.【1】According to the writer, what was the most exciting thing during the Labor Day?A.Catching fish.B.Visiting relatives.C.Enjoying natural view.D.Tasting delicious food.【2】When did the writer go catching fish with his/her uncle and cousin?A.In the morningB.In the evening.C.In the afternoon.D.The next day.【3】What does the underlined word "ones" in the third paragraph refer to?A.pondsB.fishesC.mealsD.baskets【4】What did the writer think of this experience?A.BoringB.TiringC.UncomfortableD.Unforgettable