3, 4, negative 6, 10 how to calculate 24

3, 4, negative 6, 10 how to calculate 24

3×｛10+【4+（-6）】｝

The sum of the first n terms of a sequence is Sn = (c + 1) - can, where C is not equal to - 1 and 0 (1). Prove that an is an equal ratio sequence
(2) Suppose that the common ratio of the equal ratio sequence an is q = f (c), the sequence satisfies B1 = 1 / 3, BN = f (bn-1) n is greater than or equal to 2, and the general term of the sequence BN is obtained

(1) S1 = (c + 1) - CA1 = A1, we can know that A1 = 1
S2=A1+A2=(C+1)-CA2=A1+A2,A2=C/(C+1)
S2-S1=(C+1)-CA2-[(C+1)-CA1]=-CA2+CA1=A2
So CA1 = (c + 1) A2, because C is not equal to - 1 and 0, A1 is not equal to 0, and A1 is not equal to A2
And there is A2 / A1 = C / (c + 1), because C is not equal to - 1 and 0, so A2 / A1 is not equal to 0
So an is an equal ratio sequence
(2) From (1), we can know that q = C / (c + 1), f (c) = C / (c + 1),
Then f (x) = x / (x + 1)
bn=f(bn-1)=(bn-1)/[(bn-1)+1] bn*(bn-1)+bn=bn-1,bn/(1-bn)=bn-1
Then when n = 2, B2 = B1 / (B1 + 1) = 1 / 4
n=3,b3=b2/(b2+1)=1/5
n=4,b4=b3/(b3+1)=1/6
Therefore, BN = 1 / (n + 2)

Use a 31.4cm long wire to form a square. Its area is {}. If it is formed into a circle, the area of the circle is {}

A 31.4cm long wire is used to form a square with an area of {61.6225cm},
31.4 △ 4 = 7.85 cm side length
7.85 × 7.85 = 61.6225 square centimeter area
If a circle is formed, the area of the circle is ()
31.4 ﹣ 3.14 ﹣ 2 = 5cm radius
5 × 5 × 3.14 = 78.5 square centimeter area

Calculation process of 23 + (- 16) - (- 7) - 17
-1 + two thirds + (- one fifth) - one sixth + one fifth

23+(-16)-(-7)-17
=23-16+7-17
=7+7-17
=-3
-1 + two thirds + (- one fifth) - one sixth + one fifth
=-1+2/3+(-1/5)-1/6+1/5
=-1/3-1/5-1/6+1/5
=-1/3-1/6
=-2/3

Given a group of data x1, X2,... Xn, the average is 3 and the variance is 6, find the average and variance of new data 3x1 + 5, 3x2 + 5,..., 3XN + 5

The average is 3 * 3 + 5 = 14
The variance is 3 * 3 * 6 = 54
These are all direct formulas

Xiaoming's living room has 40 square meters, with a side length of 0.8 meters of square tiles, 60 is enough

Each tile area is 0.8 m * 0.8 m = 0.64 m2, 40 m2 / 0.64 M2 = 62.5 pieces, so it is not enough

The minimum value of (x ^ 2-3x + 1) / (x-3) is obtained by means of inequality

（x^2-3x+1）/（x-3）=(x-3)+1/(x-3)+2>=2[(x-3)/(x-3)]^(1/2)+2=4

What is the original function of (arcsinx) ^ 2?

-2x+2sqrt(1-x^2)arcsinx+x(arcsinx)^2

The square in the figure below is divided into four identical rectangles, each of which has a circumference of 40 cm?

Let the side length of a square be x (x + 14x) × 2 = 4054x × 2 = 4054x = 20x = 16, then the perimeter of a square is 16 × 4 = 64 (CM). Answer: the perimeter of a square is 64 cm

Mathematics problems in grade two of junior high school
There are only two right
1. Congruent triangles have the same shape
2. The perimeter and area of congruent triangles are equal
3. If two obtuse angle triangles are congruent, then the opposite side of the two obtuse angles is the corresponding side
Please write the reason

1 pair
2 pairs
There can only be one obtuse angle for each triangle. Naturally, the opposite side of the two obtuse angles is the corresponding side