求下列这些题目的正解！谢谢各位大虾们

2022-08-10 16:39:05 分类：养花问答来源: 日夏养花网作者: 网络整理阅读：104

一些数学题，有点儿急，各位大虾们帮忙接一下吧！

1.4x-2=3x-9，求x的值。只要得数rn2.已知y=y①-y②，y①与x²成正比例，y②与x+3成反比例，且当x=0时，y=2，x=3时，y=0，求y与x的函数关系式。（要过程！）rn3.有一项工作，甲乙合作需要36天，甲丙合作需要45天，乙丙合作需要60天，求甲乙丙各自独做都各需要多少天？（列方程，还有过程！）

1.4x-2=3x-9，求x的值。
x=-7
2.已知y=y①-y②，y①与x²成正比例，y②与x+3成反比例，且当x=0时，y=2，x=3时，y=0，求y与x的函数关系式
y=y①-y②=ax²-b/(x+3)
x=0时，y=-b/3=2，x=3时，y=0=9a-b/6=0，
b=-6,a=-1/9
y=-x²/9+6/(x+3),x≠-3
3.有一项工作，甲乙合作需要36天，甲丙合作需要45天，乙丙合作需要60天，求甲乙丙各自独做都各需要多少天？
设甲、乙、丙分别需要的天数为x,y,z,即他们每天可以完成工作的1/x,1/y,1/z
1/x+1/y=1/36
1/x+1/z=1/45
1/y+1/z=1/60
解得x=60,y=90,z=180
得到甲单独完成工作需要60天，乙要90天，丙要180天

1、x=-7
2、设y①=k①x²，y②=k②/x+3，由x=0，y=2可得k②=-6；由x=3，y=0可得k①=-1/9
所以有y=-x²/9+6/x+3
3、设甲乙丙单独做各需x、y、z天，则
1/x+1/y=1/36
1/x+1/z=1/45
1/y+1/z=1/60
解方程可得x=60，y=90，z=180天

1.x=-7
2.y=ax²+b/(x+3)
当x=0时，y=2，2=b/3，b=6
x=3时，y=0，9a+1=0，a=-1/9
所以关系式为：y=-x²/9+3/(x+3)
3.设甲，乙，丙各需要x，y，z天
1/x+1/y=1/36
1/x+1/z=1/45
1/y+1/z=1/60
解得：x=60，y=90，z=180

1. -7
2.设y①=mx²+n,y②=a/(x+3)+b
当x=0时，y=2，得n=2 ， a/3+b=2 (1)
当x=3时，y=0，得m=-2/9 ，a/6+b=0 (2)
由 (1)(2)得 a=12，b=-2
得y=(-2/9)x²+2-[12/(x+3)-2]
整理得y=(-2/9)x²+4-12/(x+3)
3.设甲乙丙各自独做各需要x,y,z天
1/x+1/y=1/36，1/x+1/z=1/45，1/y+1/z=1/60
得x=60 y=90 z=180

1. x=-7
2. 设y①=kx2，y②=t（x+3），所以y=y①-y②=kx2-t（x+3）
列出关系式：当x=0时，y=2时， 2=-3t 所以t=-2/3
x=3时，y=0时，0=9k-6t 。把t=-2/3代入，得k=-4/9
所以y=-4/9x2-（-2/3）（x+3）=-4/9x2+2/3x+2
3. 设甲单独做需要x天，乙单独做需要y天，丙单独做需要z天
x+y=1/36
x+z=1/45
y+z=1/60
求方程，得y=90，z=180，x=60

1.解：4x-2=3x-9
4x-3x=-9+2
x=-7

2.解：设y①=ax²,y②=b/(x+3),y=ax²-b/(x+3).
0-b/3=2 ①
9a-b/6=0 ②
因为 b/3=-2 b=-6
把 b=-6代入 ②
得 9a+1=0 a=-1/9
所以y=-x²/9+6/(x+3).

3.解：设这项工程为1，甲单独做需X天，乙需Y天，丙需Z天，则甲每天能完成1/X,乙每天完成1/Y，丙每天完成1/Z.
1/X+1/Y=1/36 ①
1/X+1/Z=1/45 ②
1/Y+1/Z=1/60 ③
①+②-③=1/36+1/45-1/60
2/X=5/180+4/180-3/180
2/X=6/180
X=60
1/60+1/Y=1/36 1/Y=1/36-1/60 1/Y=5/180-3/180 1/Y=2/180 Y=90
1/90+1/Z=1/60 1/Z=1/60-1/90 1/Z=3/180-2/180 1/Z=1/180 Z=180
答：甲需60天，乙需90天，丙需180天。

请问这道线性代数题目怎么解，求详细解释，谢谢大佬们啦

简单计算一下即可，答案是B

两个都非0，如果其中一个是可逆矩阵，则乘积肯定非0，所以只能B对

求以下英语题目的正解

December 13th, 2005rnDear Sirs,rnrnI am very happy to apply for the position of secretary, which you adve日夏养花网rtised in China Daily of December 10, 2005.rn I havenmkHK been working as a secretary at a college office. Because I am the only secretary in the office, it is necessary for me to work quickly and efficiently and to be flexible in my daily work, Professors value my work and my ability to meet their needs.rn Although I am happy now, I feel that my promotion is limited here, and I would like to have a more challenging job. Therefore, I enrolled in a program to expand my knowledge of international business affairs. Now, both my English and Chinese have been improved and I am ready to begin working as a bilingual secretary in an international company like yours, and I believe I can be a great help to your firm.rnThe second resume gives further details of my qualifications, and I would appreciate it if you could give me an opportunity to have an interview. I am looking forward to receiving your call at 62428866 or please use the enclosed pre-paid postcard to send me your reply. Thank you very much for your consideration.rn Faithfully yours,rn Mary Leernrn1. The writer wants to change her job because ___________.rnA. she has difficulty handling her daily work efficiently rnB. she can hardly get a chance to be promoted rnC. she finds her present job too challenging rnD. she is tired of her duties at the college rn2. In order to prepare herself for a more satisfactory job, the writer ___________.rnA. has taken part in special business program rnB. tries to get the professors’ high praises rnC. has worked much harder on her job rnD. has to prove herself to be efficientrn3. A bilingual secretary (Line 4 Para. 3) differs from other secretaries in that he or she can ____________.rnA. operate a computer B. do the job efficiently rnC. speak two languages D. write official documents rn4. The writer of the letter enclosed a pre-paid postcard to ___________.rnA. request a written reply B. make an appointment rnC. get more information D. express her thanks rn5. By sending this letter, the writer expected to __________.rnA. draw the attention of the company rnB. get an opportunity for an interview rnC. apply for a suitable position in China Daily rnD. obtain more information about the companyrnrn阅读题，谢谢各位大侠

1. B 由Although I am happy now, I feel that my promotion is limited here可知。
2．A 由http://www.rixia.ccTherefore, I enrolled in a program to expand my knowledge of international business affairs
3．C 由my English and Chinese have been improvedwww.rixia.cc 可知
4．A 由I am looking forward to receiving your call at 62428866 or please use the enclosed pre-paid postcard to send me your reply可知
5．C 由第一句可知

希望能帮到你

1.B
2.A
3.C
4.A
5.B

1.B
2.A
3.C
4.A
5.B

IELTS G类考题?

初一的一道数学题，请各位大虾们解解看，辛苦了o(∩_∩)o...哈哈

题目是：有一种“24”点游戏，其游戏规则是这样的：任取一副扑克牌，我们约定A为1，J，Q，K分别为11，12，13，并规定红色牌为正，黑色牌为负。任取4张牌，将这4张牌的数字进行加减乘除四则运算（每个数用且只用一次）使其结果等于24，rn 例如，对红桃A，红桃2，方块3，方块4可作运算（1+2+3）4=24.（注意上述运算与4（1+2+3）=24应视作相同方法运算）rn 现有4张扑克牌红桃3，黑桃6，方块4，方块10，运用上述规则写出3种不同的运算式：rn (1)( )rn (2)( )rn (3)( )rn (4)另有4张扑克牌红桃3，黑桃5，梅花J，方块7，可通过运算式（），使其结果等于24.rn 标注：被人不会打横线，只www.rixia.cc用括号代替，请各位海涵o(∩_∩)o...哈哈

3,-6,4,10
4-(-6)*10/3=24
3*(-6+4+10)=24
3*(10-4)-(-6)=24

3,-5,-11,7
[-5-7*(-11)]/3=24

(10-6+4)*3=24
(10-4)*3-(-6)=24
4-10*(-6/3)=24
[-5-7*(-11)]/3=24

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