2025年暑假作业本大象出版社七年级数学人教版第39页答案
1. 若一个二元一次方程的一个解为$\left\{\begin{array}{l} x= 2,\\ y= -1,\end{array} \right. $则这个方程可以是
$x + y = 1$
(只要求写出一个).

答案

答案不唯一，如 $ x + y = 1 $
2. 下列方程:①$2x-\frac {y}{3}= 1$;②$\frac {x}{2}+\frac {3}{y}= 3$;③$x^{2}-y^{2}= 4$;④$5(x+y)= 7(x+y)$;⑤$2x^{2}= 3$;⑥$x+\frac {1}{y}= 4$. 其中是二元一次方程的是
①④
(填序号).

答案

①④
3. 方程$4x+3y= 20$的所有非负整数解为
$ \begin{cases} x = 2, \\ y = 4, \end{cases} \begin{cases} x = 5, \\ y = 0 \end{cases} $
.

答案

$ \begin{cases} x = 2, \\ y = 4, \end{cases} \begin{cases} x = 5, \\ y = 0 \end{cases} $
4. 若方程组$\left\{\begin{array}{l} 4x-2y= k+1,\\ x-y= 2\end{array} \right. $的解x和y满足$x+y= 0$,则k的值为
5
.

答案

5
5. 宾馆有二人间、三人间、四人间三种客房供游客租住,某旅行团20人准备同时租用这三种客房共7间,如果每个房间都住满,租房方案有
2
种.

答案

2
6. 一瓶牛奶的营养成分中,碳水化合物含量是蛋白质的1.5倍,碳水化合物、蛋白质与脂肪的含量共30g. 设蛋白质、脂肪的含量分别为x g、y g,可列出方程为(
A
)
A.$\frac {5}{2}x+y= 30$
B.$x+\frac {5}{2}y= 30$
C.$\frac {3}{2}x+y= 30$
D.$x+\frac {3}{2}y= 30$

答案

A
7. 已知$\left\{\begin{array}{l} x= -1,\\ y= 0\end{array} \right. 和\left\{unitable3 \right. 都是方程y= ax+b$的解,则(
B
)
A.$\left\{\begin{array}{l} a= -1,\\ b= -1\end{array} \right. $
B.$\left\{\begin{array}{l} a= 1,\\ b= 1\end{array} \right. $
C.$\left\{\begin{array}{l} a= -1,\\ b= 1\end{array} \right. $
D.$\left\{\begin{array}{l} a= 1,\\ b= -1\end{array} \right. $

答案

B
8. 若方程组$\left\{\begin{array}{l} 4x+3y= 14,\\ kx+(k-1)y= 6\end{array} \right. $的解中x,y的值相等,则k为(
C
)
A.4
B.3
C.2
D.1

答案

C
9. 若方程组$\left\{\begin{array}{l} 2a-3b= 13,\\ 3a+5b= 30.9\end{array} \right. 的解为\left\{unitable10 \right. 则方程组\left\{unitable11 \right. $的解为(
D
)
A.$\left\{\begin{array}{l} x= 8.3,\\ y= 1.2\end{array} \right. $
B.$\left\{\begin{array}{l} x= 10.2,\\ y= 0.2\end{array} \right. $
C.$\left\{\begin{array}{l} x= 10.3,\\ y= 2.2\end{array} \right. $
D.$\left\{\begin{array}{l} x= 6.3,\\ y= 2.2\end{array} \right. $

答案

D
10. 《九章算术》中记载:“今有共买羊,人出五,不足四十五;人出七,不足三. 问:人数、羊价各几何?”其大意是:今有人合伙买羊,若每人出5钱,还差45钱;若每人出7钱,还差3钱. 问:合伙人数、羊价格各是多少? 设合伙人数为x,羊价为y钱,根据题意,可列方程组为(
A
)
A.$\left\{\begin{array}{l} y= 5x+45,\\ y= 7x+3\end{array} \right. $
B.$\left\{\begin{array}{l} y= 5x-45,\\ y= 7x+3\end{array} \right. $
C.$\left\{\begin{array}{l} y= 5x+45,\\ y= 7x-3\end{array} \right. $
D.$\left\{\begin{array}{l} y= 5x-45,\\ y= 7x-3\end{array} \right. $

答案

A