Given the set a = {x | x ^ 2-1 = 0}, B = {x | x ^ 2-2ax-b = 0}, if B ≠ an empty set and B is contained in a, find the value of a and B?

Given the set a = {x | x ^ 2-1 = 0}, B = {x | x ^ 2-2ax-b = 0}, if B ≠ an empty set and B is contained in a, find the value of a and B?

Given the set a = {- 1,1}, B = {X / x ^ 2-2ax + B = 0}, and B is contained in a, find the value of a, B and the conditions

When B is an empty set, 4A ^ 2-4b

Given that x belongs to R, if inequality 8 (X-2 ax) (above) is greater than 8 (- 2x-a Square) (above) is constant, then the value range of real number a is

From the single increment of 8 ^ x, we can see that x ^ 2-2ax > - 2x-a ^ 2 is constant
That is: x ^ 2 + (2-2a) x + A ^ 2 > 0
If we regard it as a quadratic function, we can know △ from it

2/1*2*3+2/2*3*4+2/3*4*5+… 2/1999*2000*2001

Consider the generality, study the relationship between 1 / [n (n + 1) (n + 2)] and 1 / N, 1 / (n + 1), 1 / (n + 2), we can see that the following formula holds:
2 / [n (n + 1) (n + 2)] = [1 / N + 1 / (n + 2)] - 2 / (n + 1)
2/(1*2*3)=1+1/3-1
2/(2*3*4)=1/2+1/4-2/3
2/(3*4*5)=1/3+1/5-2/4
2/(4*5*6)=1/4+1/6-2/5
2/(5*6*7)=1/5+1/7-2/6
.
2/(1997*1998*1999)=1/1997+1/1999-2/1998
2/(1998*1999*2000)=1/1998+1/2000-2/1999
2/(1999*2000*2001)=1/1999+1/2001-2/2000
Add up the above 98 formulas and study the relationship between the front and back terms on the right side of the equation,
＝1/2+1/2000+1/2001-2/2000
=1/2+1/2001-1/2000
Please verify the final result yourself

In the past few years, I have learned a lot of English words?

I have learnt/learned many English words in the past/last few years

First n terms of arithmetic sequence {an} and Sn = - N & # 178; + N, find the first term of arithmetic sequence

The first term of arithmetic sequence = S1 = - 1 ^ 2 + 1 = 0

(- 2x ^ 3Y) ^ 2 (XY) ^ 3 (calculation)
(- 2x ^ 3Y) ^ 2 (XY) ^ 3 (calculation)
(x + y) ^ 2-x ^ 2 (factorization)

(- 2x & # 179; y) &# 178; (XY) &# 179; (calculation)
=4x⁶y²x³y³
=4x⁹y⁵
(x + y) ^ 2-x ^ 2 (factorization)
=(x+y+x)(x+y-x)
=(2x+y)y

Simple calculation of one half minus one third multiplied by one half plus five sixths
Specific formula

I think there are three answers
1、(1/2-1/3)x1/2+5/6=1
2、1/2—1/3x1/2+5/6=7/6
3、1/2—1/3x（1/2+5/6）=5/18

How many angles are formed when three straight lines intersect each other (not intersecting at one point)? How many pairs of opposite vertex angles? How many pairs of apposition angles? How many pairs of internal stagger angles?

12 corners, 4 around each intersection
There are 6 pairs of vertex angles and 2 pairs around each intersection
If there is no parallel line, there are apposition angle and internal stagger angle, which can not be found temporarily. The definition is as follows for reference only:
Apposition angle: two angles on the same side of the section and on the same side of the truncated line
Internal angle: the two corners on either side of the cut line or within the cut line
Inside corner: two corners on the same side of the cut line and within the cut line
The sides of the same angle form the "F" shape, the sides of the inner staggered angle form the "Z" shape, and the sides of the same inner angle form the "U" shape

Does the limit of multivariate function [Lim XLN (1 + XY)] / (x + y) x → 0, y → 0 exist?

lim(x->0) xln(1+xy)/(x+y)=0
lim(y->0) xln(1+xy)/(x+y)=0
lim(x->0+,y->0)=lim(x->0-,y->0)=0
Limit existence