Math problems, urgent! Ask for a detailed process. Reason.

Let the whole project be 1, according to B C 9 days to complete 5 8, then all the completion needs to be completed, and it takes days to complete. and C takes 24 days to complete, and B alone takes 36 days to complete. It takes 12 days to cooperate according to A and B, then it takes 18 days for A to complete it alone.

A fee = 18 * 1200 = 21600

B fee = 36 * 500 = 18000

C cost = 24 * 800 = 19200

If the project is completed in one month, then choose C.

It's over, it's a waste of brains. It's not easy to earn some points.

Let me answer: Solution: C completes 1 24 every day, that is, it takes 24 days to complete it alone.

B completes (5, 8-9, 24) 9=1, 36 per day, i.e. 36 days to complete alone, (more than 30 days, so it is excluded).

A completes 1 12-1 36=1 18 per day, i.e. it takes 18 days to complete alone.

The cost of A alone is 18 * 1200 = 21600 yuan.

C needs to complete it separately at a cost of 24 * 800 = 19,200 yuan.

It is more possible to choose Team C to save money and can complete it within the stipulated time.

According to the question, this question cannot be calculated, only team C can be known in the conditions, and the remaining two teams do not know how long it will take to complete the project, and the answer needs to be which engineering team... That's only an estimate.

The calculation conditions assume that the work efficiency is the same as the charge, then the total project quantity is the dead quantity, and the most expensive one is directly selected to complete it as quickly as possible, so that the project can be put into operation as soon as possible.

If the calculation condition assumes that the work efficiency is not linked to the fee, and it is conditionally known that the two teams of B and C can complete the work in one day, and C alone needs 24 days, then the workload of team B can assist in completing the corresponding day but it takes days, and it can be assumed that the time required by C alone is 36 days, more than one month, and team B is abandoned. The total charge of C should be 24*800=19200.

The cooperation between A and B is completed in 12 days, and the cost of these 12 days is 12*(1200+500) A and B = 20400, which cannot be calculated because the work efficiency ratio of A and B is not known.

At the same time, after the completion of the construction of the project, the daily output value is not known, so the difference between the advance date and the economic benefit can not be obtained.

Summary, cannot be calculated.

C: 1 day: 1 24 = > 9 days: 9 24 (3 8) = > B 9 days: 5 8-3 8 = 1 4

B 1 day: 1 4 9 = 1 36 = > B takes 36 days;

B 12 days = 1 3

A 12 days = 2 3 = > B takes 18 days;

Alone: A 21,600 yuan; B 18,000 yuan; C: 19,200 yuan.

It is completed within one month, and B does not meet the requirements, so C should be done.

C 1 24 i.e. 24 days to complete.

B = (5 8-9 24) 9 = 1 36 i.e. 36 days to complete (36>30) [excluded].

A = 1 12-1 36 = 1 18 i.e. 18 days to complete.

The cost of A = 18 1200 = 21600 yuan.

C cost = 24 800 = 19,200 yuan.

Interest = Principal Interest Rate Time).

1. Saving year by year:

30,000 yuan).

30540 yuan).

2. One-time deposit:

30,000 yuan).

Because the yuan is 31296 yuan, the one-time access is more accounting.

Brush the problem? Brush experience? Count me in a....

The first root number is the same as the second root number, multiplied by 3, multiplied by the starting 3, which is 9 times 3 to the 3rd power, which is the last root of 9 times.

1 ： log 7 4 = log 7 2^2 = 2log 7 2 = b

So log 7 2 = b 2

log 7 3 + log 7 2 + 1= log 7 3*2 + log 7 7= log 7 6*7

log 7 42

i.e. A + B2 + 1 = Log 7 422: LGAB = 5 = LGA + LGB i.e. LGA = 5 - LGB

And because lga *lgb = 6

So (5 - lgb)lgb = 6, i.e. (lgb) 2 - 5lgb +6 =0, the solution gives lgb = 2 or 3

So, when LGB = 2, LGA = 3, i.e. A = 1000 , B = 100

When LGB = 3, LGA = 2, i.e. A = 100 , B = 1000

3: Vedic theorem.

lga + lgb = -2

lga * lgb = -4

The solution gives lga = -1 - root number 5 lgb = -1 + root number 5 or lga = -1 + root number 5 lgb = -1 - root number 5 lga + lgb = lgab = -2, so ab = 1 100

4: From Veda's theorem.

x1 + x2 = m

x1*x2 = 3

So lg(x1+x2) (lgx1+lgx2)= lgm lg3

2 i.e. lgm = 2lg3 = lg3 2 = lg9, so m = 9

1)log7(42)=log7(3*14)=log7 (3)+log7(14)=log7(3)+log7(2)+log7(7)=a+b/2+1

2) LGAB=LGA+LGB=5, LGA*LGB=6 Treat LGA,LGB as the two roots of the equation x 2-5x+6=0LGA=2,LGB=3 or LGA=3,LGB=2A=100,B=1000 or B=100,A=10003)LGA+LGB=-2

lgab=-2

ab=1/100

4)x1+x2=m,x1x2=3

Original: lgm lg3=2

lgm=2lg3

lgm=lg9m=9

7 4=b

log 7 4=log 7 2^2=2log 7 2=b∴log 7 2=b/2

log 7 42=log 7 (6*7)=log 7 6+log 7 7=log 7 (2*3)+log 7 7

log 7 2+log 7 3+log 7 7=b/2+a+1,lga•lgb=6

lgab=lga+lgb=5

lga=5-lgb

Substitute LGA LGB = 6

There is LGB(5-LGB)=6

5lgb-(lgb)^2-6=0

lgb-2)(lgb-3)=

LGB=2 or LGB=3

b = 100 or b = 1000

When b=100, a=1000

When b=1000, a=100

3.It is known that LGA and LGB are the two roots of the equation x2+2x-4=0, and the value of AB is LGA+LGB=-2, so LGA+LGB=LG(A*B)=-2, so AB=1 100

4.It is known that x1 and x2 are the two roots of the equation x2-mx+3=0, and lg(x1+x2) lgx1+lgx2=2, find the value of m.

There are x1+x2=m, x1x2=3

lg(x1+x2)=lgm

lgx1+lgx2=lgx1x2=lg3

lg(x1+x2) lgx1+lgx2=lgm lg3=2, so m=9

1 km is x 100 liters.

So y km is xy 100 liters = 45 liters.

y=4500/x，x>0

From the meaning of the title, we can see that 45 y=x 100 is simplified to y=4500 x ,x>0

1.The current i is inversely proportional to the resistance r, let i = x r

Substituting r=5 i=2 into the equation yields x=10

i=10/r

, substituting to i=10 r, r=20 ohms.

1.Solution: Set A kind of drink X yuan per bottle, B kind Y yuan per bottle;

y-x=12x+3y=13

The solution is x=2y=3

2.Solution: 2a-b=3x(2)-3x+5

2a=b+3x（2）-3x+5

x（2）-x-1+3x（2）-3x+5

a=2x（2）-2x+2

Original = 43Solution: Xiaohong:

Let's set the fourth day to be the number X.

7x=84x=12

So the time to go out should be the 9th.

Xiaoqiang: Since the number of days in a week can only be a multiple of 7, the number of months can only be July.

According to the above explanation, it can be seen that he is the number 15. Finished.

1.Let the unit price of A be x and the unit price of B y

A system of column equations. y-x=1

2x+3y=13, please solve it yourself.

Solution: 2a-b=3x(2)-3x+5

b = x 2-x-1, substituting b into the above equation, then.

a=(3x 2-3x+5+x 2-x-1) 2=2(x 2-x+1)a-2b=2(x 2-x+1)-2(x 2-x-1)=4) Xiaohong No. 9 went out.

84 + 1 + 2 + 3 + 4 + 5 + 6-7) 7 = 14 (No.) Xiaoqiang went home on July 14.

3:84 7=12 is the number in the middle; These seven numbers are . Little Red 9 went out.