The known set a = {x | x > 15, or X

The known set a = {x | x > 15, or X

Draw a number axis
(1) If B is an empty set, then a intersects B = an empty set, then M + 1 > 2m-1, M

In the triangle ABC, the angle c is equal to 90 ° and find a point on BC so that the distance from point d to AB is equal to the length of DC

The bisector of BAC intersects BC with D

Let v be the set of upper triangular matrices of order n over the number field F. it is proved that V is a linear space under matrix addition and multiplication
And find out the dimension of V

It is only necessary to explain that V is closed to the addition and multiplication of matrices
The sum of two upper triangular matrices is still upper triangular
A number multiplied by an upper triangular matrix is still an upper triangular matrix
So V is a linear space
Its dimension is n + (n-1) +... + 1 = (n + 1) n / 2

For senior high school mathematics compulsory 2 Chapter 2 the position relationship between point, line and plane exercise 2.3 A,
It's better to send me the answers in the analysis book

You have to send the questions to me

Definite integral of DX (1 + cos ^ 2x) from 0 to Pai (2)

∫(0→π/2) dx/(1 + cos^2x)= ∫(0→π/2) dx/[(sin^2x + cos^2x) + cos^2x]= ∫(0→π/2) dx/(sin^2x + 2cos^2x)= ∫(0→π/2) dx/[cos^2x(2 + tan^2x)]= ∫(0→π/2) d(tanx)/(2 + tan^2x)= (1/√2)arctan[(tanx)...

English translation
Passing between the North and the South Island Cook discovered the east of Austria more or less by accident.
He was hanged for telling lies when he came back home.
Do not paste translation software, that I used, very messy

Cook happened to find East Austria between the north and South Islands
He was hanged for lying when he returned home

By solving the equation
A machine produced by a machinery factory used to produce a machine with 1.8 tons of steel. After the technological innovation, 0.6 tons of steel can be saved every day. Now how many tons does it take to make a machine?
How many steel products can we produce now

If x sets can be produced now, there are:
（1.8-0.6）X=36x1.8
The solution is x = 54
A: now it can produce 54 machines
Hope to adopt!

How to write the calculation formula of rectangular area?

Rectangle area = length by width
S=ab

Find the power of 3x-1 of function 3 = x + 1 of function 9

(3x-1) power of 3 = (x + 1) power of (3 & # 178;)
The (3x-1) power of 3 = the (2x + 2) power of 3
Then:
3x－1=2x＋2
3x－2x=2＋1
x=3

A is 15 years older than B. five years ago, a was twice as old as B. B is ()
A. 30 years old B. 20 years old C. 15 years old D. 10 years old

Suppose B is now x years old, then 5 years ago a was (x + 15-5) years old, B was (X-5) years old