Brothers and sisters who are good at math help me think about it. Urgent

(3x-6)/(2x+1)=0

So 3x-6=0 x=2

x 2/2 x +1>0

x 2>0 so 2x+1>0 x>-1 2

x^2>0

x-2<0 x<2

That is, 2x-4=3x+3

x=-73.Set to produce an average of x machines per day, instead of x-50.

600/x=450（x-45）

x = 180 units.

4.This harvester harvests 150x hectares of wheat per hour, and the farmer harvests x hectares per hour.

10/150x+1=10/100x

x = 30 harvesters mow 450 hectares per hour.

5.The average driving speed for the previous hour was x

180/x-2/3=（180-x）/

x=60km/h

Done, PS: I'm GG

1) 2 The numerator is equal to 0

2) x> -1 2 makes the numerator greater than 0

3) x<2 makes the numerator less than 0

2(x+1)^-1 = 3(x-2)^-12(x+1) = 3(x-2)x=8

Today, an average of x machines are produced per day.

600/x = 450/(x-50)

Get x=200

Set up this harvester to harvest x hectares of wheat per hour.

10 x + 1 = 10 (100x 150) gives x=5, and assumes the average speed of the previous hour to be x km hours.

180 x - 2 3 = (180-x) +1 gives x=60

You have to do your homework during the winter vacation.

Hehe, you just choose the upstairs, it's very hard.

The basic properties (alphabetical representation) of inequalities are given first

Nature 1: If a>b, then ac >b c

Property 2: If a>b, c>0, then ac>bc (or a>b c) property 3: if a>b, c<0, then ac1) denominates (using the inequality property).

2) Remove parentheses.

3) Shifts (using the property of inequality 1).

4) Merge similar items.

5) Convert the coefficient of the unknown to 1 (using the property of inequality).

With this type of question, it's much easier for you to draw a diagram.

Solution: (1) Let point p be (x,y), then the coordinates of point e are (-a,y).The coordinates of f are (

Because the P point is on the perpendicular bisector of EF, PE=Pf

x+a(x+a)=(x-a)(x-a)+y*y

The trajectory equation for p is y*y=(x+a)(x+a)-(x-a)(x-a).

4ax2) proof; Let the coordinates of a be (y1*y1 4a,y1)b(y2*y2 4a,y2) c(y3*y3 4a,y3).

The slopes of ab and ac add up to 0

y2-y1)(y2*y2-y1*y1)+(y3-y1)(y3*y3-y1*y1)=0

It can be simplified to obtain y2+y3+2y1=0

y2+y3=-4a

The slope of BC is k=4a(y3-y2) (y3*y3-y2*y2)=4a (y3+y2)=-1

So the BC slope is a fixed value.

The abscissa of a point a above the x-axis on the curve m is a, and the crossing point a makes two straight lines with complementary inclination angles, and the other intersection points with the curve m are b and c, respectively

1. The weight of table salt is x kilograms.

3(x－24)=x＋28

3x－72－x=28

2x=100

x = 50 kg.

The two bags of salt A and B originally weighed 50 kilograms.

2. There are x tricycles.

3x＋2(15－x)=40

3x＋30－2x=40

x = 10 tricycles with 10.

Then there are 15 10 = 5 bicycles.

1, now A = (24 + 28) (3-1) = 26kg;

It turns out that A has: 26 + 24 = 50kg; Equation solution

Solution: Let the original A and B have xkg; According to the meaning of the title,

x+28=3×(x-24)solution, x=50;2. Solution: If there are x tricycles, then there are 15-x bicycles;

3x+2×（15-x）=40；solution, x=10;Bicycles: 15-10 = 5;

This is a problem of solving a univariate equation.

Let the original mass of A and B be x kg, then (x+28)=3*(x-24) can be solved.

This is a problem of a system of binary equations, which belongs to the same cage of chickens and rabbits.

Set up x tricycles and y bicycles.

x+y=15,3*x+2*y=40.

(1) Solution: Let A and B each have x kilograms. 3 (x-24) = x283x-72 = x282x = 100x = 50 Answer: .

2) Solution: Set up x tricycles and 15-x bicycles. 3x2(15-x)=403x30-2x=40x=10A: .

sn=3n²+n

s(n-1) = 3(n-1) + n-1).

an=sn-s(n-1)=6n-2 (n2)and s1=3*1 +1=4=a1

an=6n-2 (n n)

Forehead ......Isn't this a sixth-grade question......?

First of all, I will review the calculation formula of the vertebral body and the cylinder body:

Conic = 1 3 * v cylinder = 1 3 * sh = 1 3 * r 2 * h (one-third r squared h).

Cylinder = sh = r 2*h (h squared of r).

The volume of elevated water is: *10 2 * cubic centimeters, that is, the volume of the vertebrae, then the height of the vertebral body is: 157 (1 3) ( *5 2) = 157*3 The process is all You should know how to do it

The cone is 1 3 of the volume of a cylinder with the same bottom and height

h=3 x x (10/5)^2 =6 cm

The volume of the rising water surface is the volume of the cone, so it is pai*(10 2) 2*h 3=pai*10 2*, and the solution is h=6cm, where pai is pi, h is the height of the cone, and 2 is the meaning of square.

6. Set the height of the plumb weight to h1 3 H=6 Note: PAI can't be typed, and 2 is roughly taken as the meaning of square.

v cone = v water.

1 3 * r cone 2h cone = *r column 2 * h water 1 3 *5 2h = *10

The solution is h=6

It's as simple as that, you can see if you take a closer look at their volume formulas.

6cm.First of all, the volume of the cone is one-third of that of the isolow cylinder, and then pay attention to the radius and straight warp!

Let the height of the aluminum hammer be x, the bottom area is the same, and the cylinder and cone of the same volume are the same, and the ratio of height is 1:3

x= cm

The hammer volume is the volume of water rising *10 *

v=sh=π5²h=50π

h=2cm

Conical aluminum hammer volume = volume of water surface rise = 10*10**

50π=5*5*π*h/3

h=6 cm

1）4*4*3*2*1=96

2) I just miscalculated this: 4*3*2*1*2-4*3=36 96-36=60

1.Four digits, that is, four positions to be filled. The thousand digits can be 1, 2, 3, 4 four choices, hundred, ten, single digits have 0, 1, 2, 3, 4 five choices, so 4 * 5 * 5 * 5

2.Since it is an even number, there are three options for the single digit 0, 2, and 4, 1, 2, 3, and 4 for the thousand, and 0, 1, 2, 3, and 4 for the hundred, and ten digits, so 3*4*5*5

1) A 2 out of 1 * A 3 out of 1 * A 3 out of 2 = 96

2) A 2 out of 1 * A 3 out of 1 * A 3 out of 2 + A 2 out of 1 * A 2 out of 1 * A 3 out of 2 = 60

！=96

When the thousand digit is 1 and the hundred digit is 0, the hundredth digit is 0.

In the same way, the thousand is 1, the hundred is 2....6 pcs.

The thousand is 1, the hundred is 3....6 pcs.

The thousand is 1, the hundred is 4....6 pcs.

And so on, there are 96 in total.

2.(5-2)!x3+(5-3)!x2=60