A few math problems won t! Guys help! Bounty 50!

Let the sum of the original series be s, then x*s=x+x 2+.x^(n+1)x-1)*s=x*s-s=x^(n+1)-1s=[x^(n+1)-1]/(x-1)

So 1+8+8 2+.8^2004=[8^(2004+1)-1]/(8-1)=(8^2005-1)/7

Sum of proportional sequences.

Equation If the proportional number is listed as a, aq, aq 2......aq n when q is equal to 1 s=an

When q is not equal to 1, s=a【1-q (n+1)】 (1-q), so 1+x+x 2+......x^n=【1-x^n+1)】/(1-x)

Let s=1+x+x2+.x n, xs=x+x 2+.x n + x (n + 1), subtract the above two formulas to obtain:

1-x)s=1-x^(n+1)，x≠1，∴s=[1-x^(n+1)]/(1-x).

i.e. 1+x+x 2+...x^n=[1-x^(n+1)]/(1-x).

Let x=8 in the above equation and get:

1+x+x^2+..x n multiplied by 1-x (x does not equal 1).

1-x^（n+1）

So the original formula = [1-x (n+1)] (1-x)1+8+8 2+.8 2004=(substitution x=8 n=2004)=(8 2005-1) 7

Sum of proportional sequences.

x^（n+1）-1]/(x-1)

The second question is to bring it in.

1-x^(n+1))/(1-x)

Simple proportional number series problems, children in the fourth grade of primary school who have taken the Olympiad know it!

Proportional series.

a＝1+x+x^2+..x^n

xa= x+x^2+..x^n+x^(n+1)x-1)a=x^(n+1)-1

a=(x^(n+1)-1)/(x-1）

In the same way, take the 8 as above.

y＝(8＾2005-1)/7

I won't, I'm only in my second year of junior high school, I'll ask when I grow up.

sinα=-3/2

ans :b

To the celery

y=1/(x+1)

Define the domain = (infinity, -1) u (-1, +infinity).Not truea=

12 meters long rope The whole rope is 8 times the length of Xiao Gang's body, so Xiao Gang's length is 12 8 = meters.

Compare the excess with your height, which is one and a half times the length of your body, so the excess is meters.

So the circumference of the trunk is (m.

Xiaogang body length = 12 8 =

Circumference of the trunk = meters.

Xiaogang body length = 12 8 = The remaining length after 3 circles is then the circumference of the trunk is (m.

Let the circumference of the trunk be x

Xiao Gang's length is 12 8=

3x+3x=

x = the circumference of the trunk is meters.

Is the interest tax calculated, and if so, multiply the upstairs calculation by 1 - interest tax.

Set the unknowns.

Let's say he saved $ x.

x+x=16000

So he paid 16,000 yuan in the village.

The two workshops worked together, and there was no adjustment in production time, so it was still independent production.

The total amount of production in one month is the sum of the production volume of the two workshops.

That is: 884 + 420 = 1304 (sets).

It's all a month, right? And it's all cooperation? Isn't that 884+420? If it's wrong, don't scold me for being hungry. Because I'm only in the seventh grade, what if you're in the 8th or 9th grade?

Anyway, it's all a month: not 884 + 420 = 1306 (sets).

cubic decimeter = 10,500 cubic centimeters. Width = 10500 divided by 30 divided by 14 = 25 cm. The width of the parts is 28 cm to 25 cm, so it can't fit.

2.Volume v = 1 cubic decimeter = 1000 cubic centimeters. Length = 1000 divided by 8 divided by 5 = 25 cm. Weight = multiplied by 1000 = 7800 grams = kilograms.

(1) It can't be loaded. cubic decimeter = 10,500 cubic centimeters, 30 * 14 = 420 square centimeters.

10500 420 = 25 cm < 28 cm.

2) 1 dm = 10 cm 10 * 10 * 10 = 1000 cubic centimeters 1000 (8 * 5) = 25 cm.

So this cuboid is 25 centimeters long.

1000*g = kg.

cubic decimeter = 10,500 cubic centimeters.

The width of the box = 10500 (30 14) = 25 cm does not fit, because the width of the box is 25 cm, less than 28 cm.

1 decimeter = 10 centimeters.

10 3 8 5 = 25 cm.

Length 25 cm.

Kilograms weigh kilograms.

(1) Solution: cubic decimeter = 10,500 cubic centimeters.

The width of the box = 10500 (30 14) = 25 cm, the root number (30 2 + 14 2) = the root number (1096), the root number (1096 + 25 2) is approximately equal to centimeters).

A: Yes. It can be placed obliquely (such as the solution, do not understand the question).

2) Solution: 1 dm = 10 cm.

10 3 divided by 8 divided by 5 = 25 (cm).

10 3 times grams) = kilograms).

A: It is 25 centimeters long and weighs kilograms.

cubic decimeter = 10500 cubic centimeters 10500 30 14 = 25 centimeters 28 is less than 25, so it can't fit.

1 * 1 * 1 = 1 cubic decimeter = 1000 cubic centimeters 1000 8 5 = 25 centimeters 1000 * kilograms.

(1) Cubic decimeter 10,500 cubic centimeters.

10500 30 14 = 25 (cm).

28 cm" 25 cm.

A: I can't fit the machine parts because the box is not wide enough.

2) 1 1 1 1 cubic decimeter 1000 cubic centimeters 1000 8 5 = 25 (centimeters).

grams) kilograms.

square decimeter = 1050 square centimeters.

1050 divided by 30 divided by 14 equals centimeters Centimeters less than 12 centimeters Answer: It can't be fitted, it should be less than 12 centimeters wide.

1 decimeter is equal to 10 centimeters.

10 times 10 times 10 is equal to 1000 cubic centimeters.

1000 divided by 8 divided by 5 equals 25 centimeters.

25 times equals 195 grams equals kilograms.

A: It is 25 centimeters long and weighs kilograms.