The math problem in the second year of junior high school is urgent, and I have to pay 5 tomorrow

1.Let x=3 give 4a+2b+c=28

2.Let x=1 get c=3

From the first question, 4a+2b=26

Let x=0 give a-b=-1

Lianlid a = 4 b = 5

a2+b2+c2=45

Turn the following equation on and merge the same kind of terms.

Finally, the coefficients of the corresponding x are equal.

Find the corresponding value.

a=4,b=5,c=2

1).4a+2b+c=28

Process 1Write it on the left and write it on the right.

2.Merge items of the same kind.

A came out. -2a+b=-3, b also comes out. a-b+c=1, c also came out with the correct solution, done.

When the phase and other workloads are completed, the oil consumption of A is (30 25) (60 10) = double the oil consumption of B.

In order to minimize fuel consumption, B should be allowed to work as much as possible, so B works for a total of 24 hours.

A total of 24 60 was completed, leaving 36 Pi Lao 60 A needed (36 60) 30 = 18 hours.

Therefore, A and B work together for 18 hours, and B works for another 6 hours.

Total fuel consumption 25 18 + 10 24 = 690 kg.

It's more complicated than having a hunger point Anyway, when you are too lazy to complete the phase and other workloads, the fuel consumption of A is (30 25) (60 10) = times that of B.

In order to minimize fuel consumption, B should be allowed to work as much as possible, so B has a total of 24 hours of construction.

B completes a total of 24 60, leaving 36 60 A needs (36 60) 30 = 18 hours.

Therefore, A and B Shenshen work together for 18 hours, and B works for another 6 hours.

Total fuel consumption 25 18 + 10 24 = 690 kg written.

Set A x hours, B y hours. (the total amount is 1) can list two formulas:

x+y is less than or equal to 24

x/20+y/60=1

The solution x is greater than the equal demolition of Li Yu 18 Because A is expensive, and he has to travel late to save money, so A should work as much as possible to celebrate and be less noisy.

When x=18, y=6

The total amount is 690 kg.

Hope it helps.

The angle dec and the angle c are mutually congruent, so we know that cd is perpendicular to de, and ab is perpendicular to de, and two straight lines perpendicular to the same line are parallel, so ab is parallel to cd

First of all, you have to understand that the inner angle of the triangle is 180°, and then, the angle AEC is congruent with the angle dec, because AE de, is 90°, and then, the angle dec is congruent with the angle C, indicating that the angle C = the angle AEC, and because the inner wrong angle is equal, the two straight lines are parallel, indicating ab cd.

Parallel: Because dec and c are redundant, d=90 degrees ab parallel cd (the isotopic angle is equal, and the two lines are parallel).

Parallel coincidence proves that the cd is perpendicular to the de

Solution: ad cdHere's why:

Because the angle ced and the angle c are redundant, so the angle ced angle c = 90 degrees so the angle cde = 180 degrees - (angle ced angle c) = 90 degrees and because ae de so the angle bed = 90 degrees so the angle cde = angle bed = 90 degrees so ab cd "Because it is a mobile phone, some symbols can't be typed, you can replace the text with symbols yourself! >

Because dec+ c=90 degrees so d=180°-(dec+ c)=90° because ae de so bed=90°, so ab cd, the inner wrong angles are equal, and the two lines are parallel.

1) Because the straight line y=-x+2 intersects with the x-axis and y-axis at a and b respectively.

So let the coordinates of a be (a,0) and the coordinates of b be (0,b).

Substituting a,b into the straight line y=-x+2 gives a=2,b=2

So the coordinates of a are (2,0) and the coordinates of b are (0,2).

2) If the coordinates of point C are (x,y), then S OAC can be based on OA and Y on the ordinate of C as the high; S obc is based on ob and high on the abscissa of c. It is also known from (1) oa=2, 0b=2

Because s oac:s obc = 2:3

So [(1 2)oay]:[1 2)obx]=2:3 i.e. (1 2 times 2y):(1 2 times 2x)=2:3

The solution is y:x 2:3 so y (2 3)x

And because S oab=s oac+s obc (1 2 times 2y):(1 2 times 2x) [1 2 times 2(2 3)x

1 2 times 2x)=1 2oa times ob 2 to get x=6 5 y (2 3) x 4 5

So the ordinate of c is (6 5, 4 5).

1.Set the coordinates of point a to (a,0).

Substituting y=-x+2.

0=-a+2

a=2, so the coordinates of point a are (2,0).

Set the coordinates of point b to (0,b).

Substituting y=-x+2.

b = 2, so the coordinate of point b is (0,2).

1) A(2,0) B(0,2) (2) Let the coordinates of point C be (m,n), so the area of the triangle OAC is OA N, and the area of the triangle OBC is ob*m, and because the triangle OAC triangle OBC=2 3, and because OA ob 2, so n M 2 3, and because point C is on AB, so C(3,2).

1) When y=0 gets x=2, that is, the line intersects with the x-axis and a(2,0) when x=0 gets y=2, that is, the line intersects with the y-axis and b(0,2)2)s oab=1 2 2 2=2, because if s oac:s obc=2:3, so s oac=2 (2+3)=2 5

Let the c coordinate be (x,y), then s oac=1 2 2 y=2 5 s oab=2 5 2

i.e. 1 2 2 y = 2 5 2

The solution is y=substitution the equation of the straight line to obtain x= i.e., the c coordinate (,

a(2,0)b(0,2) c(6/5,4/5)

In the first problem, when x y is equal to zero, the second can be set k, and the abscissa can be found first and then the function is brought in.

1. The two straight lines are parallel, indicating that the slopes are equal, so that k=-1 3 so y=-x 3+b

And because the line y=-x 3+b and the line y=(-2x+1) 3 intersect at the same point on the y-axis, it means that the two lines intersect at x=0, and b=1 3 is found at this time, so the analytical formula of the line is y=-x 3+1 3=(1-x) 3.

2. Select a (k<0, b>0 image).

Let me answer: Let us have x units transported from place A to home and (16-x) units to place B; There are (15-x) units transported from B to A, and [13-(16-x)] units transported to B (x-3). The total cost is $y.

According to the question: y=500x+400(16-x)+300(15-x)+600(x-3).

400x+9100

Because x-3 0, x 3, y increases with the increase of x, when x takes 3, y has a minimum value, 16-x=13, 15-x=12, that is, it is transported from a to 3 in a place, 13 in a place, 12 in a place and 0 in a place B from a place, and the total cost is the most economical.

The topic is poor.

1.Solution: If the withered water from reservoir A to place A is x million tons, then the withered water from reservoir A to place B is (14-x) tons; If the withered water of reservoir B to place A is y tons, then the withered water of reservoir B to place B is (14-y) tons.

And x+y=15 So the total amount of withering is: 50*x+30*(14-x)+60*y+45*(14-y) =50*(x+y)+10*y+(30+45)*14-30*(x+y)-15*y =50*15+10*y+75*14-30*15-15*y=1350-5*y (where 0<=y<=14 To get the minimum value, y=14 should be taken, so the designed withering scheme is 10,000 tons of water from reservoir A to place A and 130,000 tons of water to place B; Reservoir B withers 140,000 tons of water to place A and 00,000 tons of water to place B. 2.

If X sets of machines are transported from A to A, then A is transported to B (16-x), B is transported to A (15-x), B is transported to B 13-(16-x) = (x-3), from the title: the total freight is 500x+400(16-x)+300(15-x)+600(x-3)=400x+9100, because x 0 and 16-x 0 and 15-x 0 and x-3 0, so x 3So when x=3, the minimum total shipping cost is 10,300 yuan.

That is, 3 machines are transported from A to A, 13 machines are transported from A to B, 12 are transported to B and 0 are shipped from B to 10,300 yuan.

Forehead... This question is not clear without drawing, and it has to be discussed in two situations, which is too troublesome and too lazy to play.

Solution: Set the original time to xThe entire engineering quantity is 1. Then:

A month to complete 1x

B completed in one month: 1 (6+x).

Equations according to the problem:

1 x+1 (6+x)] 4 (x-4) (6+x)=1 Solve this equation to obtain: x=12 (months).

Let A take x months, then B will take x+6 months, a total of four months, 1 x times 4 plus 1 (x+6) multiplied by 4, and the rest of the days B has worked for x-4 months and the amount of work done is (x-4) multiplied by 1 (x+6).

4 x + 4 (x+6) +x-4) multiplied by 1 (x+6) = 1

The situation of cooperation can be understood in this way: that is, the work of April that A helps with is equivalent to the work of more than six months of work of B. In other words, A is twice as efficient as B. If A takes x months to complete the work, then B will take months to complete, and x=12 is obtained. Hehe.

The last item, A and B two teams first work together for 4 months, and the rest is constructed by B team alone, which is just completed on schedule, that is, if team B works alone, after the time, the rest will be completed by A in 4 months, and if B does it, it will take 6 months, that is, if the work efficiency of the workers is the same, then A is 6 4 = times the number of people B. Team A's construction alone can be completed on time, which proves that if B only completes 1 after the construction alone, and the remaining 1 3 will be completed in 6 months, then the first 2 3 will take a year.

That is, it takes a year and 12 months to build a road.