Ask for a math problem, ask for a math problem

1) Let the coordinates of point A (x,y)x*y=6,y=-2x+8, the answer is a1(1,6); a2(3,2)

2) Let the quadrilateral area be z, z=x*y=-2x +8x, the maximum value of this function will be found, and bring x in to see if it is a square.

Solution: A1 middle school is transferred to A2 middle school X1 color TV (if X1 is negative, it is considered that A2 middle school is transferred to A1 middle school|.)x1|Taiwan color TV, the same below).

A2 Middle School transferred to A3 Middle School X2 color TVs; A3 Middle School transferred to A4 Middle School X3 color TVs; A4 Middle School transferred to A1 Middle School X4 color TV. �

Because there are a total of 15+8+5+12=40 color TVs, an average of 10 units per school.

15-x1+x4=10,8-x2+x1=10,5-x3+x2=10,12-x4+x3=10

x4=x1-5,x1=x2+2,x2=x3+5,x=x4-2

x4=x1-5,x2=x1-2，x3=x2-5=x1-2-5=x1-7

And this question requires y=|x1|+|x2|+|x3|+|x4|=|x1|+|x1-2|+|x1-7|+|x1-5|minimum value. where x1 is an integer satisfying -8 x1 15.

Let x1=x, consider the function y=|, defined on -8 x 15x|+|x-2|+|x-7|+|x-5|.

x|+|x-7|Represents the sum of the distances from the number x to 0 and 7, and when 0 x 7, |x|+|x-7|Obtain a minimum value of 7;

In the same way, when 2 x 5, |x-2|+|x-5|The minimum value of 3 is obtained, so when 2 x 5, y takes the minimum value of 10, that is, when x = 2, 3, 4, 5, |x1|+|x1-2|+|x1-7|+|x1-5|Take the minimum value of 10

Therefore, the minimum total number of color TVs is 10

Seek satisfaction.

Solution: If you travel x kilometers per hour in the afternoon, then you will travel (x+5) kilometers per hour in the morning 3 (x+5)+2x=340

x=65A: 65 kilometers per hour in the afternoon and 70 kilometers per hour in the morning.

70 km in the morning and 65 km in the afternoon.

70 km/h in the morning and 65 km/h in the afternoon.

Column equation: Let the afternoon speed x

2x+3(x+5)=340

x = 71 kmh, 76 kmh a.m.

A planar Cartesian coordinate system can be established, with a(0,0),b(x1,y1),c(,p(m,n).

i.e. vector cb=(x1-x2,y1-y2).

Vector pb (x1-m, x2-n).

x1-x2, y1-y2) = x(-m, -n) + (x1-m, x2-n) i.e. x1-x2 = -xm + x1-m

m=x2 (1-x).

y1-y2=-xn+y1-n

n=y2 (1-x).

p(x2/(1-x),y2/(1-x))

Vector Pa = (x2 (X-1), Y2 (X-1)) Vector AC = (X2, Y2).

i.e. vector ac=vector pa*(x-1).

The vector AC is collinear with the vector PA.

The point p must be on the line where the AC edge is located.

Vector CB = X vector PA + vector PB

Deformation into vector cb - vector pb = x vector pa

That is, the vector cp = x vector pa

So the vector cp and the vector pa are collinear vectors.

That is, C, P, A three points are collinear.

The point p must be on the line where the AC edge is located.

The picture is a 7-sided shape, and another unangled angle = angle 7 + angle 8 + angle 9

So it is actually the inner corner of the 7-sided shirt or the shape of the collapse key. So yes. Pick B

The sum of the angles is the last inner angle of the heptagon.

Looking at the picture, it should be a 7-sided shape, Wang Ze.

Another unmarked angle = angle 7 + angle 8 + angle 9

So it's actually a 7-sided trap that lets the inner corners of the shed slide and.

So it is 7*180-360=900° to choose B

When Li Ming and Wang Hua met for the first time, it was a full journey, and the second time they met, it was a full journey of three together, (you can draw a picture to see clearly), when the first time they met, Li Ming walked 52 meters, and when the two met for the second time, the two walked three full courses, then Li Ming should walk three 52 meters, 52 * 3 156 meters, these 156 meters plus 44 meters, that is, 2 full courses, so: (156 + 44) divided by 2 100 meters,

From the question, it can be seen that the sum of the distances traveled by the two of them is 3 times the distance between the two places, and the distance between the two places is x meters.

And the distance traveled by Li Ming is x+52 meters, and the distance traveled by Wang Hua is x+44 meters.

x+52+x+44=3xx=96 meters.

96m.Set the armor speed to aB's velocity is b, and A's time to walk 52m is 52 a

At this time, B takes b*(52 a), the total distance is 52+b*(52 a), and in the same way, there is a total distance a*(44 b)+44=52+b*(52 a), so that a b=x, the solution is x=11 13, and substituting one of the formulas gives a total distance of 96m

The first time Li Ming and Wang Hua's displacements were 52, x-52 From this time to the second time, Li Ming and Wang Hua's displacements were x-52 + x-44 2x-96, 96 and they are all at a constant speed, so 52 x-52 2x-96 96 get x 100, it's really not easy to write these on the phone, you really asked me a question,

That is, in another minute, it will catch up. So is the speed difference in a minute of the driving distance:

The two cars are kilometers apart.