How to calculate 40% x + 21 = 37x-78% x = 2.2x + 30% x = 26 (1-25%) x = 1540% X-30 = 152x + 20% x = 3.3 jijiji 40%x+21=37 x-78%x=2.2 x+30%x=26 (1-25%)x=15 40%x-30=15 2x+20%x=3.3

How to calculate 40% x + 21 = 37x-78% x = 2.2x + 30% x = 26 (1-25%) x = 1540% X-30 = 152x + 20% x = 3.3 jijiji 40%x+21=37 x-78%x=2.2 x+30%x=26 (1-25%)x=15 40%x-30=15 2x+20%x=3.3

40%x+21=37x=（37-21）÷40%x=40x-78%x=2.2x=2.2÷（1-78%）x=10x+30%x=26x=26÷（1+30%）x=20(1-25%)x=15x=15÷（1-25%）x=2040%x-30=15x=（15+30）÷40%x=112.52x+20%x=3.3x=3.3÷（2+20%）x=1.5

2 / 3 of a number is 17 less than 20. What is the number? (calculation by formula)

I'm Kitty 35,
（20－17）÷2/3＝4.5

-81 / 9 simplification
This is how to simplify the score

-81/9=-9

How to judge the positive and negative of a + C according to the image of quadratic function

It means the positive and negative of a and C
The opening upward indicates a > 0, and the opening downward indicates A0
The point of intersection with Y-axis at the origin indicates C = 0
The point of intersection with Y-axis is on the negative half axis of y-axis

Calculation: (1 / 2 + 1 / 3 +...) +1/2006）（1+1/2+1/3+…… +1/2005）-
:(1/2+1/3+…… +1/2006）（1+1/2+1/3+…… +1/2005）-（1+1/2+1/3+…… +1/2006）（1/2+1/3+…… +1/2005）
Why is there no sign in the middle? How to calculate

Let 1 / 2 + 1 / 3 + +1/2006=a,1/2+1/3+…… +1/2005=b
Then, the original formula is a (1 + b) - (1 + a) B
=a+ab-b-ab
=a-b
Substituting a and B, we get
a-b=1/2006

Given the set a = {x ∈ Z | 2 ≤ 2 ^ (2-x) 1}, then the number of elements in the set a ∩ (CRB) is
A．0
B．1
C．2
D．3
"2" is the subscript of log, and notice that it has an absolute value. "A ∩ (CRB)" is the intersection of a (the complement of B)

2¹≤2^(2-x)

About line segments (21 8:58:44)
1. The bus between a and B stops at three stops, and the fare is the same
(1) How many different fares are there?
(2) How many kinds of tickets should I prepare?
2. It is known that A.B. is an obtuse angle. A.b.c.ding calculated 1 / 6 (a + b) of the results, which are 26 degrees, 50 degrees, 72 degrees and 89 degrees respectively, only contain the correct results. Then who do you think the correct results may be given? Give your reasons

There are 10 kinds of tickets and 20 kinds of tickets
There are 4 + 3 + 2 + 1 = 10 kinds of fares at the 5 stations of permutation and combination 0-0-0-0-0. This is the way to go
There are 10 kinds of tickets, but the ticket price is the same, the ticket price is different
So there are 10 kinds of tickets and 20 kinds of tickets
2 A. B are obtuse angles, so 180

X ^ 2-4y ^ 2 + x-2y factorization factor

x^2-4y^2+x-2y
=(x^2-4y^2)+x-2y
=(x+2y)(x-2y)+(x-2y)
=(x+2y+1)(x-2y)

The solving process of X - (1 / 3x + 1) = 27
It's the equation of this problem. I don't know if I'm right
How many meters is the total length of a piece of iron wire

x-1/3x-1=27
2/3x=28
x=42

Calculate the determinant
1 2 3 …… n
2 2 0 …… 0
3 0 3 …… 0
..........
n 0 0 …… N find the answer of Dai Yuejin's version of linear algebra

This is a claw determinant, can be turned into a triangle, as shown in the figure