The four numbers 0 1 2 3 can be used to form one bit integer, two bit integer, three bit integer and four bit integer There are () natural numbers which are multiples of 3

The four numbers 0 1 2 3 can be used to form one bit integer, two bit integer, three bit integer and four bit integer There are () natural numbers which are multiples of 3

0,3,12,21,30,102,120,123,132,201,210,213,231,312,321,1023,1032,1230,1320,1203,1302,2013,2031,2103,2130,2301,2310,3012,3021,3102,3120,3201,3210
Don't forget. There's another zero
There are 33

Who told me the range of real numbers, rational numbers, integers and natural numbers

Real numbers include rational numbers and irrational numbers,
Rational numbers include integers and fractions,
Integers include positive integers, 0 integers and negative integers,
Positive integers and 0 are also called natural numbers
They are all infinite sets, not from

Let the quadratic function f (x) = (K-4) x2 + KX (K ∈ R) hold for any real number x, f (x) ≤ 6x + 2
(k-4)x^2+(k-6)x-2

You have solved (K-4) x ^ 2 + (K-6) X-2 ≤ 0
This inequality can be understood as that the function value of (K-4) x ^ 2 + (K-6) X-2 is always less than 0, and this is a parabola. Only when the opening is downward and Δ is less than zero, the whole image of the parabola will be below the X axis, and the function value will always be less than 0. You can draw a sketch to see it for easy understanding

d∫arctan[sqrt(x)] dx=?

∫ arctan√x dx = ∫ ƒ(x) dx = F(x) + C
d(∫ arctan√x dx)dx
= d[F(x) + C]/dx
= ƒ(x)
= arctan√x

Find the rule: 3 / 97,1 / 15,9 / 83,3 / 19,5 / 23, (), ()

3/97,1/15=6/90,9/83,3/19=12/76,5/23=15/69
Add 3 to the numerator and subtract 7 from the denominator
The last two are 18 / 62 = 9 / 31 and 21 / 55

What are the two natural numbers adjacent to n?

n-1 ,n+1

What are the natural numbers
What is the minimum natural number

Natural number means the number of objects, 0 means none, so the integer of natural number starting from 0 is: 0,1,2,3 The smallest natural number is 0

9 / 4 / 18 / 6 / 27 / () / ()

9、4、18、6、27、（8）、（36）
I provide a rule: odd items are increased by multiple of 9, 9, 18, 27, 36
Even term is a multiple of 2, 4, 6, 8
There may be other rules!

The product of four consecutive integers is 7920. Find the four numbers

7920 = 2 × 2 × 2 × 3 × 3 × 5 × 11, 2 × 2 × 2 = 8, 3 × 3 = 9, 2 × 5 = 10, so 7920 = 8 × 9 × 10 × 11. A: among the four numbers, 8, 9, 10, 11

It is known that f (x) satisfies f (- x) + F (x) = 0 on R, and is an increasing function on [0, + ∞]. If f (1 / 2) = 1, then - 1

F (x) + F (- x) = 0 → f (x) = - f (- x) - > F (x) is an odd function on R, f (0) = 0
Because f (x) increases monotonically at (0, + OO)
So f (x) increases over R
f(-1/2)=-f(1/2)=-1
-1=f(-1/2)