Given that the sum of the first n terms of the arithmetic sequence {an} is Sn, and S2 = 10, S5 = 55, then the coordinate of a direction vector of the line passing through P (n, an) and Q (n + 2, an + 2) (n ∈ n *) is () A. (2，12)B. (−12，−2)C. (−12，−1)D. （-1，-1）

Given that the sum of the first n terms of the arithmetic sequence {an} is Sn, and S2 = 10, S5 = 55, then the coordinate of a direction vector of the line passing through P (n, an) and Q (n + 2, an + 2) (n ∈ n *) is () A. (2，12)B. (−12，−2)C. (−12，−1)D. （-1，-1）

The sum of the first n terms of the arithmetic sequence {an} is Sn = A1 · n + n (n − 1) 2D, from S2 = 10, S5 = 55: 10 = 2A1 + d55 = 5A1 + 10d solution: A1 = 3, d = 4, then PQ = (2, an + 2-An) = (2, 8) analyze the four answers: (− 12, − 2) is a direction vector of PQ, so choose B

If x2 + MX + 25 is the complete square of X, then M=______ ．

∵ x2 + MX + 25 is the complete square of X, ∵ M = ± 10

In the rectangular coordinate system, the coordinates of vertex A and B of triangle ABC are (- 1, - 2), (3, - 2), respectively, and the fixed point C moves on the straight line y = x + 2
(1) When the area of △ ABC is 6, try to find the coordinate of point C
(2) When △ ABC is an isosceles triangle with ab as its base, the coordinate of point C is obtained

Coordinates of point C (x, x + 2)
AB^2=[3-(-1)]^2+[-2-(-2)]^2=4^2
AB=4
1, the linear equation of AB: y = - 2, y + 2 = 0
Distance from C to ab: 2 * s (ABC) / AB = 2 * 6 / 4 = 3
The formula of distance from point to straight line is: axo + BYO + C │ / √ (A & # 178; + B & # 178;) = | 1 * (x + 2) + 2 | / 1 = 3, x = x = - 1
y=x+2=-1+2=1
Coordinates of point C (- 1,1)
2, AC^2=(x+1)^2+(x+2+2)^2=2x^2+10x+17
BC^2=(x-3)^2+(x+2+2)^2=2x^2+2x+25
AC=BC, AC^2=BC^2
2x^2+10x+17=2x^2+2x+25
x=1 y=x+2=1+2=3
Coordinates of point C (1,3)

If x + 1 power of 2 × x + 1 power of 3 = 36, find X

(2*3)^(x+1)=36
6^(x+1)=6^2
x+1=2
x=1

Compare the size of 999.111 to 99.11 to 9

999 / 1111 Max
99 / 111 medium
9 / 11 minimum

Minimum value of 4x & # 178; + Y & # 178; - 2y-4x + 15

When (2x ^ 3 3x ^ 2y-9xy ^ 2) - 0.5 (6x ^ 2Y 4x ^ 3) = 2x ^ 3 3x ^ 2y-9xy ^ 2-3x ^ 2y-2x ^ 3 = - 9xy ^ 2, y = - 2 and y = 2, y ^ 2 is 4, so when y = 2 and y = - 2,

A small motor connected to 220 V power supply, known coil resistance is 20 ohm, how much power is the motor consumption
This is the second question. The first question is when the current of the input motor is 2
A, what is the input power of the motor

The first question is voltage multiplied by current, that is, 220 * 2 = 440 W, that is, the input power is equal to 440 W. the second question is that when the motor is working, the consumed electric energy is mainly converted into mechanical energy, so the motor does not belong to "pure resistance" ("pure resistance" means that all the work done by the current is heated, and all the electric energy is converted into internal energy)

The polynomial 3x2-2xy-y2-x + 3y-5 is divided into two groups. The two brackets are connected by a negative sign, and the first bracket contains x term

3x2-2xy-y2-x+3y-5=（3x2-2xy-x）-（y2-3y+5）．

An electric kettle marked "220V 1.1KW", for:; resistance of the kettle; same point 10 Miao, heat generated by the electric kettle
An electric kettle marked with "220V 1.1KW" works under rated voltage. Requirements: the current passed by the electric kettle when it works normally; the resistance of the kettle; the heat generated by the electric kettle at the same point

I = P / u = 1100 / 220a = 5a, current 5 a
R = u / I = 220 / 5 ohm = 44 ohm, resistance is 44 ohm
Q = w = Pt = 1100 * 10J = 11000j, the heat generated is 11000 joules (excluding heat loss)

Fifth grade volume two mathematics on the general points of a little difficult questions, to answer and analysis

8 out of 29 and 5 out of 116
321 / 116, 5 / 16
Analysis: 116 and 29 are multiple relations, so we should use 116 to divide (denominator)
Many students think it's a coprime relationship. 29 is a prime number. It's easy