Asking for a mathematical formula should be simple

Because 1+2+.50 can be seen.

There are 25 51s in total, so 25*51 is fine.

Or all lined up.

There are a total of 50 pairs of 51, but they are repeated, for example, 1+50=51 and 50+1=51 are repeated pairs, so 51*50 2

Note a=1+2....50

It can also be written as a=50+.2+1

Two additions (the first number is added to the first number, and the second is added to the 2nd.) 2a=（1+50）+（2+49）+.50+1) Note that the parentheses are all equal.

So a

The sum of the first and last terms is equal to 50 + 1 = 51

The summing formula, sum = (first term + last term) * number of terms 2

Equation for summing the difference series = (first term + last term) * number of terms 2

Number of items = (first term - last term) Tolerance + 1

The formula for calculating the difference series is used.

This is an elementary school math Olympiad talked about in the equal difference number series ball and common is.

SUM = (first term + last term) * number of items 2

The formula for calculating the difference series.

Commonly used mathematical formulas:1. The area of the rectangle is long and wide, and the calculation formula is s=ab.

2. The area of the square is the length of the side and the length of the side, which is calculated by the formula s=a a=a2.

3. The circumference of the rectangle (length and width) 2, the calculation formula c=(a+b) 2.

4. The circumference of the square is 4, and the calculation formula is c=4a.

5. The area of the parallelogram is the height of the bottom of the cavity, and the calculation formula is s=ah.

6. The area of the triangle is 2 at the bottom, and the formula is s=a h 2.

7. The trapezoidal area (upper and lower bottom) is 2, and the calculation formula is s=(a+b) h 2.

8. The volume of the cuboid is length, width and height, and the calculation formula is v=abh.

9. The area of the circle Pi radius squared, calculated by the formula v= r2.

10. The volume of the cube is the length of the edge, the length of the edge, the length of the edge, and the calculation formula v=a3.

11. The volume of the cuboid and the cube can be written as the base area is high, and the calculation formula is v=sh.

12. The volume and bottom area of the cylinder are high, and the calculation formula is v=sh.

13. The number of copies of each copy The total number of copies The number of copies The number of copies The number of copies The number of copies The number of copies of the total number of copies.

Multiples Multiples Multiples 1 Multiples Multiples Multiples 1 Multiples.

15. Speed Time Distance Speed Time Distance Time Speed.

16. Unit price, quantity, total price, unit price, total quantity, total price, quantity, unit price.

17. Work efficiency Working hours Total work efficiency Total working hours Total working hours Working hours Work efficiency.

18. Add the number of additions and and add one addition to the other.

19. Subtracted subtraction difference is dismantled and rounded subtraction difference subtraction difference subtraction subtraction.

20. Factor Factor Product One Factor Another Factor.

21. Dividend, divisor, divisor.

Rectangle circumference with acacia empty length: (length + width blindness) *2

Rectangle area: length * width.

Parallelogram area: base * height.

Triangle area: base * height 2

Circumference of the circle: straight diameter * pi.

Rectangle volume: length * width * height.

This is the k-representation of the random variable for the independence test.

In daily life, analyze whether there is a relationship between two variables, and construct a random variable under the assumption that there is no relationship (ho).

k = n(ad-bc) (a+b)(c+d)(a+c)(b+d),n=a+b+c+d, statisticians have found that in the case of ho is true, p(k, that is, in the case of ho is true, the probability of k exceeding the observed value is very small, it is a small probability event, then ho is asserted that ho is not true.

This method of using the random variable k to determine that "two categorical variables are related" is called the independence test.

Sine theorem: In the triangle ABC, a sina = b sinb = c sinc, where a, b, c are trigonometrics, and a, b, c are opposite sides.

Cosine theorem: In the triangle ABC, C 2 = A 2 + B 2-2 Abcosc Stuwart's theorem: M is a point on BC, then (AB 2*CM+AC 2*BM BC)-BM*CM=AM2

Menelaus's theorem and Seva's theorem (very important but complicated to check for yourself) Fermat's theorem: if p is a prime number, (a, p) = 1, then a (p-1) = 1 (mod p).

x=x/6+x/12+x/7+5+x/2+4=?

Is it to find how much x is? If it is, the first pass on the right.

x=14x 84+7x 84+12x 84+42x 84+9, then x=75x 84+9

Shift x-75x 84=9

9x 84=9

x=84

？？？What's the problem? How do I know if you don't say?

Divide the right side of the formula, and then multiply the denominator to the left, and simplify both sides.

2r=620

2r=160

r=r-r=230

n=δr (total number of turns, 255 due to practical problems) l=2 (255r+(1+244)*244*total length) (the radius of each circle is added, the radius of the first circle is r, a total of 255 circles, and the radius of the last circle is r+244*, the sum is summed by the formula).

2* meters.

The radius of the outer ring is 620 2 = 310mm, the radius of the inner circle is 160 2 = 80mm, and the annular area is s=310*310*

Set the roll x, straighten the tape to a rectangle, the rectangular area is also s, and get s = 310 * 310 *

Solve x = i.e., to roll rice.

Ring area formula: s= (r*r-r*r).

Rectangle area formula: s=a*b

First lap: 160*

Second Lap: (160+.)

Lap 3: (160+.)

The nth circle: (160+, will: 160+ solve n=256 and sum it with a sequence...)

It is equal to multiply (310 squares minus 80 squares) divided by about meters.

Analysis: The problem is converted into a number of small rings, and the diameter of the small rings increases by the total length l= d1+ d2+·· dn = n(d1+dn) 2 , the use of array companies.

From the meaning of the question, we can find n=(dn-d1) (2*take 256 and bring in the formula for the handlet: l=

Ask what is the formula of a mathematical formula (a+b) to the nth power.

is the binomial theorem:

a+b）^n=a^n+c¹n*a^(n-1)b+c²n*a(a-2)b²..b^n.