Brothers and sisters a new problem math please do how, thank you

1)a3=a1+2d、a6=a1+5d。

a1+2d)^2=a1(a1+5d)

a1^2+4a1d+4d^2=a1^2+5a1d4a1d+4d^2=5a1d

Because d<>0, 4a1+4d=5a1

a1=4d=1、d=1/4。

an=1+(n-1) 4=(1 4)n+3 4, n is a positive integer.

2)bn=16/[(n+3)(n+4)]=16[1/(n+3)-1/(n+4)]

sn=16[1/4-1/5+1/5-1/6+…+1/(n+3)-1/(n+4)]=16[1/4-1/(n+4)]=4n/(n+4)

1.The square of a3 = a1*a6, a3 = a1 + 2d = 1 + 2d. (d is the tolerance), a6 = a1 + 5d = 1 + 5d, substituting the first formula in the previous one to get: 1 + 4d + 4d square = 1 + 5d, calculate d = 1

2.Question 2: No.

1) Let the tolerance be d: then the general formula is an=a1 +(n-1)d, because: a3=1+2d, a6=1+5d, a3*a3=a1*a6, get: d=1 4

an=1+（n-1）1/4

2) I can't understand the second question.

a3=a1+2d a6=a1+5d

a1*a6=a3^2

a1*(a1+5d)=(a1+2d )^2d=a1/4

Because an is an equal difference series, an=a1+(n-1)d can be substituted to an=a1*(n+3) 4

Substitute the previous formula into bn:

bn=16a1[1 (n+3)-1 (n+4)]The first n terms and the middle n terms of bn are added and subtracted, leaving the head and tail.

bn=16a1[1/(1+3)-1/(n+4)]=16a1[1/4-1/(n+4)]=4a1-16a1/(n+4)

Let me tell you what to think. (1)a1*a6=a3*a3 .a6=a1+5d ,a3=a1+2d.

So a1*(a1+5d)=(a1+2d)*(a1+2d)It can be solved a1=4d.So d=1 4....

an=n/4+3/4.

2)bn=1 (n 4+3 4)(n 4+1)=4 so sn=4* hope...

1. If the pen is set to be $x, the pencil is $6-x.

2(6-x)+4x=23，2x=11

x=, 6-x=

Pencil element, pen element.

2. Set 50 yuan tickets to buy x tickets, then 40 yuan tickets to buy 40-x tickets.

50x+40*(40-x)=1850

10x=250

x=2540-x=15

There are 25 tickets for 50 yuan and 15 tickets for 40 yuan.

3. If A stores x tons of grain, then B is 95-x tons.

95-x)*(1-40%)=2x*(1-2/3)2x/3+

19x/15=57

x = 45 A stocks 45 tons of grain, B stores 50 tons of grain.

4. Let these two tens of digits be x, then the single digit is 9-x.

100x+9-x=6*(10x+9-x)

99x+9=54x+54

45x=45

x=1,9-x=8

The two-digit number is 18

5. Set x two-pointers to make a free throw 14-3-x.

3*3+2x+(14-3-x)=28

x = 8 two-point shots and 14-3 - x = 3 free throw shots.

6. Set up mountain roads x kilometers. The flat road takes (55 60-x 12) hours.

1 hour 10 minutes = 70 minutes, 1 hour = 60 minutes.

x/6+55/60-x/12=70/60

x/12=15/60

x=3 The flat road takes 55 60-x 12=2 and the circle 3, and the flat road is 9*2 3=6 km, so the camp is 3+9=12 km away from the school.

Categories: Education Academic Exams >> Study Help.

Problem description: 1. A large box with a cuboid shape, 24 decimeters long, 18 decimeters wide, and 12 decimeters high, with a small box of cubes inside. If you want to make the box just full, without going beyond the hole and not wasting space, what is the maximum edge length of the small box? 2. A batch of table tennis balls should be packed in several bags, if each bag contains 5, 6, and 7 respectively, there will be 4 of them.

How many ping-pong are there in this batch?

Analysis: The greatest common divisor is 6, so the length of the leak detection edge of a small box is 6 decimeters.

2. Suppose you take out 4 in the bag, it becomes a multiple of , and the least common multiple of is 210, so this batch of table tennis balls has at least 210 + 4 = 214.

This is a proportional sequence of finding the sum of the first n terms.

Solution: Set the price of the first year to be $x.

x(1 (solution x.)

** per square meter is 10,000 yuan.

A: The starting price is 10,000 yuan per square meter in the first year.

Just set the unit price of the pavement in the first year to x square per meter, and then list the equation and solve the equation.

x+(1+%5)x+(1+%5)x*(1+%5)+(1+%5)x*(1+%5)*(1+%5)+…88 40 Add 15 times in total, sorry I only have the first Chinese.

Wzchenyichu, hello :

Analysis: 0 on the unit price of a product is missing, and I am ready to pay 28 yuan, which means that the unit price of this product has been reduced by 10 times, and only 1 copy of the money is counted.

The price of this item is Perpeg is:

55 28) (10 1) 10 30 (Yuan Cons only) The ** of another item is:

55 30 25 (yuan).

x+y=28

x+10y=55

The solution is x=25, y=3

Therefore, the unit price of the two goods is 25 yuan and 30 yuan.

Answer, one is 30, the other is 25, let two unknowns, list two equations, and solve it.

If Xiao Chen has x books, then Xiao Lin has (23-x) copies and Xiao Li has (29-x) copies, which are derived from the title, 29-x) + (23-x) = 24

29+23-2x=24

52-2x=24

2x=24-52

2x=-28

x=(-28)÷(2)

x=14 solves x=14, so (23-x)=9, (29-x)=15, answer: Xiao Lin has 9 books, Xiao Chen has 14 books, and Xiao Li has 15 books.

The three of them have a total of: (23 29 24) 2 38 (Ben) Then, Xiao Li has: 38 23 15 (Ben).

Kobayashi has: 38 29 9 (Ben).

Xiao Chen has: 38 24 14 (Ben).

Kobayashi 9 copies.

Xiao Chen 14 copies.

Xiao Li 15 copies.

You can assume that Xiao Lin has 10 copies, Xiao Chen has 13 copies, and Xiao Li has 16 copies, but Xiao Li and Xiao Lin don't agree. Therefore, Kobayashi's number cannot be higher than 10. If you assume that Xiao Lin has 9 copies, Xiao Chen is 14 copies, and Xiao Li is 15 copies, so it is just right.

3 people have a total of (23+29+24) 2=38

Xiao Lin 9, Xiao Chen 14, Xiao Li 15

Solution: Set Xiaolin to have x books.

23-x＋（24-x）＝29

47-2x＝29

2x＝-18

x 9 Xiao Chen: 23-x 14 (Ben).

Xiao Li: 24-x 15 (Ben).

x+23-x+23-x+x+x+6+x+x+6=76 (Solution: Let Kobayashi have x book).

2x+58=76

2x=18x=99+6=15 (Ben).

23-9=14 (Ben).

Answer: Xiao Lin has 9 copies, Xiao Li has 15 copies, and Xiao Chen has 14 copies.

Kobayashi 9 Ko Chan 14

Xiao Li 15 welcome to ask.

Why is it negative, this can be explained by the relationship of trigonometric functions to the unit circle. Think of this clock as a unit circle, and the ordinate is represented by y=sin(xt+y), but x here refers to the speed of the second hand along the counterclockwise. So this w is negative.

And y is a fixed value, don't worry about it. Got it?

Because y=sin(t+) is the angle inside the parentheses, the angle has been decreasing over time due to the clockwise rotation. This requirement can only be met if it is negative.

Hello, the location is located in the fourth quadrant.

I didn't figure it out carefully!

Hope it works for you!

The definition of the book is counterclockwise as positive, and go to the book.

Of course it's negative, go clockwise and subtract A

Pages 1-9, 9.

10-99 pages, 90*2=180

100-695 pages, 596*3=1788

How many numbers are used: 9 + 180 + 1788 = 1977 (pieces), of which the number 5 is used:

Pages 1-9, 1.

10-99 pages, 9+10=19.

100-695 pages, 6 * (19 + 1) + 100 = 2201 + 19 + 220 = 240 5

1-9 9 pcs.

10-99 90*2=180.

Total = 9 + 180 + 1500 + 288 = 206710 + 10 = 20 single digits + tens digits.

100-499 The same goes for 4*20=80.

600-695 20 pcs.

A total of 5 has 20+80+120+20=240

Pages 1-9, 9.

10-99 pages, 90*2=180

100-695 pages, 596*3=1788

How many numbers to use in total: 9 + 180 + 1788 = 1977 (pieces) of which the number 5 is used: Okay.