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

The triangle inequality theorem states that the sum of any two sides of a triangle must be greater than the length of the third side. If a triangle has side lengths of 6 and 12, which inequality represents the possible lengths, x, of the third side of the triangle?
原库参考解析
Linear inequalities in one or two variables · 原库模块 1 · Q9作答 ↗
线性不等式与可行域挑战

On a car trip, Rhett and Jessica each drove for part of the trip, and the total distance they drove was under 220 miles. Rhett drove at an average speed of 35 miles per hour (mph), and Jessica drove at an average speed of 40 mph. Which of the following inequalities represents this situation, where r is the number of hours Rhett drove and j is the number of hours Jessica drove?
原库参考解析
PSAT 8/9 P1 · 原库模块 3 · Q2作答 ↗
线性不等式与可行域进阶

For a party, 50 dinner rolls are needed. Dinner rolls are sold in packages of 12. What is the minimum number of packages that should be bought for the party?
原库参考解析
PSAT 8/9 P2 · 原库模块 1 · Q9作答 ↗
线性不等式与可行域基础

During spring migration, a dragonfly traveled a minimum of 1,510 miles and a maximum of 4,130 miles between stopover locations. Which inequality represents this situation, where d is a possible distance, in miles, this dragonfly traveled between stopover locations during spring migration?
原库参考解析
PSAT 8/9 P2 · 原库模块 2 · Q15作答 ↗
线性不等式与可行域进阶

A number x is at most 17 less than 5 times the value of y. If the value of y is 3, what is the greatest possible value of x?
原库参考解析
PSAT10 P1 · 原库模块 1 · Q19作答 ↗
线性不等式与可行域挑战

题目图表
The shaded region shown represents the solutions to which inequality?
原库参考解析
PSAT10 P1 · 原库模块 2 · Q12作答 ↗
线性不等式与可行域挑战

A cleaning service that cleans both offices and homes can clean at most 14 places per day. Which inequality represents this situation, where f is the number of offices and ℎ is the number of homes?
原库参考解析
PSAT10 P1 · 原库模块 2 · Q1作答 ↗
线性不等式与可行域基础

题目图表
The shaded region shown represents solutions to an inequality. Which ordered pair (x,y) is a solution to this inequality?
原库参考解析
PSAT10 P1 · 原库模块 3 · Q16作答 ↗
线性不等式与可行域基础

Monarch butterflies can fly only with a body temperature of at least 55.0 degrees Fahrenheit °F. If a monarch butterfly's body temperature is 51.3°F, what is the minimum increase needed in its body temperature, in °F, so that it can fly?
原库参考解析
PSAT10 P1 · 原库模块 3 · Q3作答 ↗
线性不等式与可行域进阶

题目图表
The shaded region shown represents the solutions to which inequality?
原库参考解析
PSAT10 P2 · 原库模块 1 · Q8作答 ↗
线性不等式与可行域基础

A geologist needs to collect at least 67 samples of lava from a volcano. If the geologist has already collected 63 samples from the volcano, what is the minimum number of additional samples the geologist needs to collect?
原库参考解析
PSAT10 P2 · 原库模块 2 · Q9作答 ↗
线性不等式与可行域进阶

The total cost, in dollars, to rent a surfboard consists of a $25 service fee and a $10 per hour rental fee. A person rents a surfboard for t hours and intends to spend a maximum of $75 to rent the surfboard. Which inequality represents this situation?
原库参考解析
机考OG1 · 原库模块 1 · Q3作答 ↗