这部分需要会什么？
- 由两点或图象求斜率
- 识别斜截式、点斜式和一般式
- 解释截距并判断平行与垂直
核心概念与公式
两点 \((x_1,y_1),(x_2,y_2)\) 且 \(x_1\ne x_2\) 时，斜率 \(m=(y_2-y_1)/(x_2-x_1)\)。它表示横坐标每增加 1，纵坐标的变化量。直线常写成 \(y=mx+b\) 或 \(y-y_1=m(x-x_1)\)。
\(y\) 截距为 \((0,b)\)；求 \(x\) 截距需令 \(y=0\)。不同非竖直平行线斜率相同；两条非竖直直线垂直时 \(m_1m_2=-1\)。竖直线 \(x=c\) 的斜率不存在，它与水平线垂直。
做题时怎样使用
- 有两点先求斜率；有一点和斜率优先用点斜式
- 需要截距时分别令另一个坐标为零
- 把所得直线代回给定点，检查坐标和单位
容易混淆的地方
斜率分子与分母必须采用相同的点的顺序。截距是坐标轴上的位置；\(y\) 截距的纵坐标才是式中的 \(b\)。
用一个例题串起方法
知识点教学例题一条直线经过 \((2,7)\) 与 \((5,16)\)。求它的方程及 \(y\) 截距。
展开解题思路 ＋
\(m=(16-7)/(5-2)=3\)。用点斜式得 \(y-7=3(x-2)\)，即 \(y=3x+1\)。因此 \(y\) 截距为 \((0,1)\)。
本知识点题库
先独立作答，再查看答案与解析。
直线方程・斜率与截距进阶
Line k is shown in the xy-plane. Line n (not shown) is perpendicular to line k and passes through the point (4, 7). Which equation defines line n?
参考答案
直线方程・斜率与截距进阶
The table gives the average time t, in minutes, it takes Adriana to travel a certain distance d, in miles. Which equation could represent this linear relationship?
参考答案
直线方程・斜率与截距进阶
For the linear function \( f \), the table shows three values of x and their corresponding values of \( f(x) \). Function \( f \) is defined by \( f(x)=rx+s \), where r and s are constants. What is the value of r+s?
参考答案
直线方程・斜率与截距挑战
For the linear function \( f \), \( f(0)=0 \) and \( f(42)=6 \). Which equation defines \( f \)?
原库参考解析
直线方程・斜率与截距挑战
What is an equation of the graph shown?
参考答案
直线方程・斜率与截距进阶
Line p is defined by \( y=2x-9 \). Line s is parallel to line p in the xy-plane. What is the slope of line s?
原库参考解析
直线方程・斜率与截距进阶
A linear function g is defined by \( g(x)=ax+b \) , where a and b are constants. If \( g(-1)=-8 \) and \( g(3)=4 \), what is the value of a?
参考答案
直线方程・斜率与截距挑战
What is an equation of the graph shown?
参考答案
直线方程・斜率与截距进阶
The table shows three values of x and their corresponding values of y. There is a linear relationship between x and y. What is the y-coordinate of the y-intercept of the line in the xy-plane that represents this relationship?
参考答案
直线方程・斜率与截距挑战
What is an equation of the graph shown?
参考答案
直线方程・斜率与截距挑战
A line in the xy-plane passes through the points (7, 1), (0, 5), and (c, 0). What is the value of c?
原库参考解析
直线方程・斜率与截距进阶
In the xy-plane, lines p and s are perpendicular and intersect at the point (-3, 4). Line p passes through the point (2, -6). What is the slope of line s?
参考答案
