On the judgment of the direction of vector outer product If the four fingers of the right hand represent the direction of W, the direction of V can be obtained in the direction of turning to R. but if the four fingers represent the direction of R, how to use the right hand screw to obtain the direction of V

Or use the right-hand spiral rule: at this time, the direction of vector V is opposite to the former

Why is the direction of vector cross product determined by the right hand rule

It's artificial

How to use the right hand rule to calculate the result of vector cross product?

The direction of vector C is perpendicular to the plane of a and B, and the direction should be judged by the "right hand rule" (the four fingers of the right hand first represent the direction of vector a, and then the fingers swing towards the palm of the hand to the direction of vector B, and the direction pointed by the thumb is the direction of vector C)
If vector a = (A1, B1, C1), vector b = (A2, B2, C2),
be
Vector a · vector b = A1A2 + b1b2 + C1C2
Vector a × vector b=
| i j k|
|a1 b1 c1|
|a2 b2 c2|
=(b1c2-b2c1,c1a2-a1c2,a1b2-a2b1)
(I, J and K are the unit vectors of three mutually perpendicular coordinate axes in space respectively)

Solution equation: X (3x-7) = 6

x（3x-7)=6
3x²-7x-6=0
3 2
1 -3
（3x+2）（x-3）=0
x1=-3/2,x2=3

Proposition p: there is a real number x, which makes the function LG (AX2 + 2x + 2a) meaningless. If P is not a true proposition, find the value range of A

(first, make it clear that non-p means
For any real number x, LG (AX2 + 2x + 2a) is meaningful
That is to say, the definition domain of LG (AX2 + 2x + 2a) is r
Then, (AX2 + 2x + 2a) is always greater than 0
Therefore, the opening is upward, △ < 0
A > 0 and 4-8a ^ 21 / √ 2)
The big brother's solution is too boring. In fact, there is a real number such that AX2 + 2x + 2a is less than o
A > 0 and 4-8a ^ 21 / √ 2 are obtained
,△< 0,

How to divide 5 / 2 by (5 / 2 + 4 / 3)

5 / 2 divided by (5 / 2 + 4 / 3)
=5 / 2 divided by 5 / 2 + 5 / 2 divided by 4 / 3
=1+15/8
=23/8

A straight line passes through P (2,1), and the angle between it and the straight line 5x-2y + 3 = 0 is equal to 45 ° to find the equation (process) of the straight line

Let the required linear equation be y = KX + B
1. Find the slope a
The angle between the straight line and 5x-2y + 3 = 0 is 45 ° and the slope of 5x-2y + 3 = 0 is 5 / 2, which can be drawn on the coordinates because only
Then we use the trigonometric formula to calculate Tan (45 + a) = (tan45 + Tana) / (1-tana * tan45) = 5 / 2
Tan45 = 1, we can find Tana = 3 / 7, K is the slope equal to Tana, so k = 3 / 7, and B = 1 / 7 because of P (2,1)
So a straight line is y = 3x / 7 + 1 / 7
In addition, there is a straight line perpendicular to y = 3x / 7 + 1 / 7, and its slope is - 7 / 3, then p (2,1) is brought in to get another line
y=-7x/3+14/3
See reference for the figure

How to write desperate English words?

It's desperately

In higher mathematics, how to obtain the power series of a function, such as Maclaurin series

The source of power series is Taylor series. McLaughlin series is a special form of Taylor series when x = 0. McLaughlin series is power series in a sense

How to calculate 2005003-2003 times 2002 by factorization

2005003-2003×2002
=2003000+2003-2003×2002
=2003×(1000+1-2002)
=-2003×(1000+1)
=-2003000-2003
=-2005003