1问题提出题目:(北师大版《义务教育教科书·数学》八年级上册“一次函数的图像和性质”第87页随堂练习3)x从0开始逐渐增大时,函数y=2x+6和y=5x-2哪一个的值先到达10,哪一个值先到达20?这说明了什么问题?学生1:令y=2x+6=10,得x=2,令y=5x-2=10,得x=2.4,所以x从0开始逐渐增大时,函数y=2x+6先到达10。令y=2x+6=20,得x=7,令y=5x-2=20,得x=4.4,所以x从0开始逐渐增大 1 questions raised the subject: (Beijing Normal University edition of “compulsory education textbooks · Mathematics” eighth grade on the “first-order function of the image and nature of” page 87 exercises 3) x gradually increasing from 0, the function y = Which of the values ​​of 2x + 6 and y = 5x-2 first reaches 10 and which of them first reaches 20? Student 1: Let y = 2x + 6 = 10, where x = 2 and let y = 5x-2 = 10, x = 2.4, so x gradually increases from 0, the function y = 2x + 6 first reached 10. Let y = 2x + 6 = 20, get x = 7, let y = 5x-2 = 20, get x = 4.4, so x starts to increase gradually from 0