Use formula n (n + 1) to calculate 100 + 102 + ······ + 200 Observation: 2 = 1 * 2, 2 + 4 = 2 * 3.2 + 4 + 6 = 3 * 4 Try to calculate 2 + 4 + 6 + +2n formula (above), and use the formula to calculate 100 + 102 + two hundred

Use formula n (n + 1) to calculate 100 + 102 + ······ + 200 Observation: 2 = 1 * 2, 2 + 4 = 2 * 3.2 + 4 + 6 = 3 * 4 Try to calculate 2 + 4 + 6 + +2n formula (above), and use the formula to calculate 100 + 102 + two hundred

It can be inferred that: 2 + 4 + 6 + +2n = n (n + 1), prove: 2 + 4 + 6 + +2n=2（1+2+3+… +n） =2*【（1+n）+（2+n-1）+（3+n-2）… 】 =2*(1+n）*n/2 =n（n+1),100+102+······+200=（2+4+6+······+200）-（2+4+6...

The result of calculating 200 * 100 ^ n is
A.2*100^2n＋2 B.2*100^n
C.2*10^2n＋1 D.2*10^2n＋2

D.2*10^(2n＋2)
200*10^n
=2*10^2*(10^2)^n
=2*10^2*10^2n
=2*10^(2n+2)

Hongqi primary school sixth grade students like sports statistics, including 48 people like football
Football 20%, rope skipping 15%, table tennis 30%, others 22.6%, shuttlecock 12.5%

48÷20%
=48÷0.2
=240

What is the square root of 5? How to express it? ± √ 5 is OK?

The square root can have positive and negative arithmetic, and the square root is positive

Number a is 200, which is 2 / 3 of number B and 50% of number C. The average number of numbers a, B and C is ()

A: 200
B: 200 △ 2 / 3 = 300
C: 200 △ 1 / 2 = 400
Average: (200 + 300 + 400) △ 3 = 300

The denominator of the equation is removed from two-thirds X-1 = 1

Multiply the equation left and right by 6
3x-2（x-1）=6
3x-2x+2=6
x=6-2
x=4

Number a is 120, number B is 15 less than number A. how many points more than number B?

120 × (1-15), = 120 × 45, = 96; (120-96) △ 96, = 24 △ 96, = 14; answer: number a is 14 more than number B

Given a > 0, b > 0 and 2A + AB + a = 30, the minimum value of function y = 1 / AB is obtained
Come on! Please pull! Thank you!

I used the universal calendar to get the result under the assumption that a is an integer, but the result surprised me
The source code is as follows
Private Sub Command1_ Click()
Dim a
Dim y, yy, b
y = 10000
For a = 1 To 15
b = (30 - 2 * a - a) / a
If b > 0 Then
yy = 1 / (a * b)
If y > yy Then
y = yy
End If
End If
Next
Print "y=";y
End Sub
No matter what the values of a and B are, the value of Y is 0.037037
So I made a simplification and got the result: y = 1 / 3 (10-A)
This function has too many solutions in the interval a belongs to (0,30), so it is impossible to solve it

The ratio of a to B is 5 to 9, and B is 22 more than A. find B

Let a be x and B be y
x/y=5/9
y-x=22
X = (5 / 9) y, i.e. Y - (5 / 9) y = 22
y=49.5
x=28.5
That is 28.5 for a and 49.5 for B

If a is a square matrix of order 6 and the number of solution vectors in the fundamental solution system of the homogeneous linear equation AX = 0 is 2, then R (a) = ()
If a is a square matrix of order 6 and the number of solution vectors in the fundamental solution system of the homogeneous linear equation AX = 0 is 2, then R (a)=
（ ）
A．2 B．3
C．4 D．5

C
R(A)=n-k
N number of unknowns
The number of k-fundamental solution system vectors