经过七八年级的学习,我们会发现,方程思想实在是中学数学的解题利器,尤其是在有计算需要的时候,如解决实际问题,在图形中求线段长度、求角度等.解决实际问题时,我们借助线段图、关系句等方式寻找等量关系来列方程,在图形中求角度时我们根据多边形内角和及角的和差积商关系来列方程,求长度时用得较多的则是根据勾股定理来列方程.现在我们学了相似,又 After seventy-eighth grade learning, we will find that the idea of ​​equation is really a high school mathematics problem solving tool, especially when there is a need for calculation, such as solving practical problems, find the length of the line segment in the graph, for perspective, etc. To solve practical problems , We use the line graph, relational sentences and other ways to find the same amount of relations to the column equation, the angle in the graphics we polygons based on the angle and the angle and sum of differential operators to rank equations, seek more length It is based on the Pythagorean theorem to formulate equations. Now we learn a similar, again