Two application questions from the first year of junior high school are in urgent need of answers

Solution: The sum of the areas of the three circles is 56, the area of the circle A and the circle c and the area of the circle b are 3 5, a+ c = 3 5 b

b＋3／5⊙b=56

b=35⊙a＋⊙b=21 35÷（1／7）=51／6⊙a＋1／3(21-⊙a)=5

a=12，⊙c=9

Answer: The areas of circles a, b, and c are respectively.

2. When x=1, its value is 5:x=2, and its value is 7:x=-2: its value is 11 and is substituted into ax 2+bx+c:

a+b+c=5 4a+2b+c=7 4a-2b+c=11 - obtained: 4b=-4 b=-1

Obtain: 8a+2c=18, 4a+c=9 c=9-4a substituting b=-1, substituting a=-1 gets: a-1+9-4a=5 a=1 substituting b=-1, a=1 into obtain:

1-1+c=5 c=5Answer: a=1,b,=-1,c=5.

1.There is a problem with the question.

b=-1 c=5

Happy New Year, thank you.

Question 1: Incompetent.

2.When x=1, a+b+c=5,

When x=2, 4a+2b+c=7,

When x=-2, 4a-2b+c=11, 8a+2c=18, 4b=-4

b = -1 substituting b = -1 to get a + c = 6

a=6-c8（6-c）+2c=18

c=5, substitution a=1

1.First of all, it is easy to calculate that the area of b is 56 times five-eighths to get 35, and let the area of a be x, there is 1 6x+1 3(21-x)=5

So a12, b35, c9

4a+2b+c=7,4a-2b+c=11, and the simultaneous solution is a=1, b=-1, c=5

1.Suppose: A cow eats x per day and decreases y

Then 40*10x+10y=30*12x+12y20x=y

The grass is always 600x, and the number of days is 2 at that time.

The grass is 600x-2y=560x, and the number of days is 2

The number of cattle is 560 x 2x = 280

2.Set: a drainage volume of one minute drainage x, water inlet of the water pipe one minute y then 3 * 45x-45y = 5 * 25x-25y

x=2y, the total amount of water is 3*45x+45y=225y

Set the time to a minute.

8ax-ay=225y

a = 15 minutes.

Answer: The second price reduction is the original price as the source refers to the J X

then 40 38 +60 x hail rush =

x = the second price is the original price.

You look at it, right?

1. Solve with a system of binary equations:

Solution: Let the speed of the train be v meters and the length of the train be l meters.

Equation 1: 10V=L

Equation 2: 40v = 1000-l

After bringing in, it is solved: l=200 meters.

v=20 m-s.

Explanation: The left side of Equation 1 represents the distance traveled by the train from the moment the locomotive just touches the bridge to the moment when the whole train has just boarded the bridge, and the right side is the length of the train. (The time for the train to be on the bridge is 40 seconds, so the upper and lower bridges are 10 seconds each).

The left side of Equation 2 represents the distance traveled by the train in a time of 40 seconds, and the right side represents the bridge length minus the train length. (The 40-second time corresponds to the process: the tail of the train is about to leave one side of the bridge until the front of the train just reaches the front of the other side, so the distance traveled is not the length of the entire bridge, but the length of the bridge minus the length of the train.)

If the locomotive is about to go up the bridge and the locomotive just gets off the bridge, the process corresponds to the time when the train has crossed the bridge. ）

2. B. Solution: A and B each roll an ordinary cube dice, and the product of the two can be even and odd as follows:

b\a 1 2 3 4 5 61 1 2 3 4 5 6

The probability of an odd number occurring is 1 in 4 (9 out of 36).

The probability of an even number is three in four (twenty-seven out of thirty-six).

Therefore, the game is in B's favor

This question examines the judgment of the fairness of the game To judge the fairness of the game, it is necessary to calculate the probability of each participant winning, and if the probability is equal, it is fair, otherwise it will be unfair The knowledge points used are: as long as the total number of cases is the same, whoever contains the most cases will have a greater likelihood; The reverse is also true; If the cases included are comparable, then they are equally probable Probability = Ratio of the number of cases sought to the total number of cases

I hope it will be helpful to the landlord.,This answer is provided by a friend.。

(1000+2x) 60=(1000-2x) 40 x=100m (1000+200) 60=20m sec.

Length: 100 meters, speed: 20 meters, seconds.

2. The odds of B winning are 50% for 2 people and 50% for 2 people to multiply the odd odd odd 3 4

1) Let the train length be L and the speed be V; 60v=1000+l；40V=1000-2L solution yields L=250m v= m/s.

2) B has a better chance of winning. Because although there are 3 odd numbers and 3 even numbers, both odd and even multiply even numbers get even numbers, and only odd numbers multiplied by odd numbers get odd numbers. Obviously, B wins bigger.

1.Solution: If the total number of students is x, then the number of boys is , then it is obtained.

x=x=n/

That is, the total number of students is n

The number of teachers is: x out x * 1 out of 11 = n out of n

2.Solution: i.e. (meta.)

1-1 Assuming that the total number of students is y, (y-n) y = 55%, y = 20n 9

1-2 The number of teachers is one-tenth of that of boys, i.e. (20n 9 - n) 10 = 11n 90

2.The total amount of money that Xiao Li brought = + 13 = +13 (yuan).

1） n/45% （n/45% ）55%×1/10 = 11n/90

2) (a 80% 18+13) yuan = +13 yuan Purely self-calculated, absolutely true.