知识点地图 / 代数

Linear Inequalities & Feasible Regions

线性不等式与可行域

正确处理不等号方向,用区间或平面区域表达满足限制的取值。

01 / UNDERSTAND

这部分需要会什么?

  • 解一元一次不等式并表示解集
  • 识别端点是否包含与边界线是否实线
  • 检验二元线性不等式的公共可行域

核心概念与公式

不等式两边加减同一个数,不等号方向不变;乘除正数方向不变,乘除负数必须反向。例如 \(-2x>6\) 等价于 \(x<-3\)。复合不等式的“且”表示交集,“或”表示并集。

二元不等式先画边界直线,再用不在边界上的测试点判断哪侧满足。\(\le\)、\(\ge\) 包含边界,使用实线;\(<\)、\(>\) 不含边界,使用虚线。可行域需同时满足全部条件。

做题时怎样使用

  1. 将文字中的至少、至多、超过分别转成对应不等号
  2. 解不等式;涉及负数乘除时特别检查方向
  3. 若变量表示人数、件数等,再在解集中选整数,并核对端点

容易混淆的地方

“至少 5”包括 5;“大于 5”不包括 5。图上的某点满足一个条件,并不代表它满足整个不等式组。

02 / CONNECT

用一个例题串起方法

知识点教学例题
一项活动收取固定费用 18 元,每位参加者另付 7 元。总预算不超过 60 元,最多可有多少位参加者?
展开解题思路 +

设人数为非负整数 \(n\),则 \(18+7n\le60\),所以 \(n\le6\)。最大人数为 6,此时费用恰好为 60 元。

03 / PRACTISE

本知识点题库

先独立作答,再查看答案与解析。

221 道题目
找到 221 道题目重置筛选
线性不等式与可行域挑战

y < 6x + 2
For which of the following tables are all the values of x and their corresponding values of y solutions to the given
inequality?

原库参考解析
Linear inequalities in one or two variables · 原库模块 1 · Q11作答 ↗
线性不等式与可行域挑战

A shipping service restricts the dimensions of the boxes it will ship for a certain type of service. The restriction states that for boxes shaped like rectangular prisms, the sum of the perimeter of the base of the box and the height of the box cannot exceed 130 inches. The perimeter of the base is determined using the width and length of the box. If a box has a height of 60 inches and its length is 2.5 times the width, which inequality shows the allowable width x, in inches, of the box?
原库参考解析
Linear inequalities in one or two variables · 原库模块 1 · Q12作答 ↗
线性不等式与可行域挑战

y > 13x -18
For which of the following tables are all the values of x and their corresponding values of y solutions to the given inequality?
原库参考解析
Linear inequalities in one or two variables · 原库模块 1 · Q13作答 ↗
线性不等式与可行域挑战

Ken is working this summer as part of a crew on a farm. He earned $8 per hour for the first 10 hours he worked this week. Because of his performance, his crew leader raised his salary to $10 per hour for the rest of the week. Ken saves 90% of his earnings from each week. What is the least number of hours he must work the rest of the week to save at least $270 for the week?
原库参考解析
Linear inequalities in one or two variables · 原库模块 1 · Q15作答 ↗
线性不等式与可行域挑战

y > 2x -1
2x > 5
Which of the following consists of the y-coordinates of all the points that satisfy the system of inequalities above?
原库参考解析
Linear inequalities in one or two variables · 原库模块 1 · Q16作答 ↗
线性不等式与可行域挑战

Adam’s school is a 20-minute walk or a 5-minute bus ride away from his house. The bus runs once every 30 minutes, and the number of minutes, w, that Adam waits for the bus varies between 0 and 30. Which of the following inequalities gives the values of w for which it would be faster for Adam to walk to school?
原库参考解析
Linear inequalities in one or two variables · 原库模块 1 · Q1作答 ↗
线性不等式与可行域挑战

A laundry service is buying detergent and fabric softener from its supplier. The supplier will deliver no more than 300 pounds in a shipment. Each container of detergent weighs 7.35 pounds, and each container of fabric softener weighs 6.2 pounds. The service wants to buy at least twice as many containers of detergent as containers of fabric softener. Let d represent the number of containers of detergent, and let s represent the number of containers of fabric softener, where d and s are nonnegative integers. Which of the following systems of inequalities best represents this situation?
原库参考解析
Linear inequalities in one or two variables · 原库模块 1 · Q2作答 ↗
线性不等式与可行域挑战

A local transit company sells a monthly pass for $95 that allows an unlimited number of trips of any length. Tickets for individual trips cost $1.50, $2.50, or $3.50, depending on the length of the trip. What is the minimum number of trips per month for which a monthly pass could cost less than purchasing individual tickets for trips?
原库参考解析
Linear inequalities in one or two variables · 原库模块 1 · Q3作答 ↗
线性不等式与可行域挑战

y\( \le \) x + 7
y\( \ge \) -2x -1

Which point (x , y ) is a solution to the given system of inequalities in the xy-plane?
原库参考解析
Linear inequalities in one or two variables · 原库模块 1 · Q4作答 ↗
线性不等式与可行域挑战

A salesperson’s total earnings consist of a base salary of x dollars per year, plus commission earnings of 11% of the total sales the salesperson makes during the year. This year, the salesperson has a goal for the total earnings to be at  least 3 times and at most 4 times the base salary. Which of the following inequalities represents all possible values of total sales s , in dollars, the salesperson can make this year in order to meet that goal?
原库参考解析
Linear inequalities in one or two variables · 原库模块 1 · Q5作答 ↗
线性不等式与可行域挑战

A number x is at most 2 less than 3 times the value of y . If the value of y is -4, what is the greatest possible value of x ?
原库参考解析
Linear inequalities in one or two variables · 原库模块 1 · Q6作答 ↗
线性不等式与可行域挑战

A psychologist set up an experiment to study the tendency of a person to select the first item when presented with a series of items. In the experiment, 300 people were presented with a set of five pictures arranged in random order. Each person was asked to choose the most appealing picture. Of the first 150 participants, 36 chose the first picture in the set. Among the remaining 150 participants, p people chose the first picture in the set. If more than 20% of all participants chose the first picture in the set, which of the following inequalities best describes the possible values of p ?
原库参考解析
Linear inequalities in one or two variables · 原库模块 1 · Q8作答 ↗