题目

（2019·北京中考模拟）已知：关于x的一元二次方程x2-4x+2m=0有两个不相等的实数根． （1）求m的取值范围； （2）如果m为非负整数，且该方程的根都是整数，求m的值． 答案：（1）m＜2；（2）m=0. 【解析】  (1)∵方程有两个不相等的实数根， ∴△＞0. ∴△=16-8m＞0. ∴m＜2 (2)∵m＜2，且m为非负整数， ∴m=0或1 当m=0时，方程为x2-4x=0，解得x1=0，x2=4，符合题意； 当m=1时，方程为x2-4x+2=0，根不是整数，不符合题意，舍去. 综上m=0 【点睛】 本题考查了学生通过根的判别式来确定一根据短文内容完成表格中所缺信息，每空限填一个单词。I had the meanest(最刻薄的) mother in the whole world.When other kids ate candies for breakfast，I had to have porridge，eggs or bread.When others had Coke and candies for lunch, I had to eat rice.And my supper was also different from other children’s.In a word, we must eat healthy food.But I wasn’t alone when I was sad.My sister and two brothers had the same mean mother as I did.My mother must know where we were all the time.She had to know who our friends were and where we were going.We had to clean clothes and take a bath every day.The other kids may wear the same clothes for days.We couldn't lie in bed“sick” in order not to go to school.We had to go to bed before 9:00 every night and get up at 7:00 the next morning . We couldn’t sleep until noon like our friends on Sundays.We had to do housework like washing dishes, making beds and cooking.Through the years，things didn't change a little.In the school we had to get good grades.What’s more,our mother didn't let us drop out of school.She decided to make us grow up into educated and honest adults.I am now trying to raise my three children this way.I am full of happiness when my children call me a mean mother.Why?Because now I thank God every day because it gave me the meanest mother in the world.I am lucky to have the 1.mother in the worldMy life as a kidMy sister,two brothers and I couldn’t have 2.foodWe must let my mother know 3.we were all the time and who our friends were.We had to go to bed and get up4.every day.We had to do 5. like washing dishes,making beds and cooking.In the school we had to get good 6..My mother never let us 7.out of school.Mother’s hopeWe were able to become educated and 8.adults.My feeling nowWhen my children call me a mean mother, I am 9. of happiness.I think God every day for 10. me the meanest mother in the world.