There are five different books, including two Chinese books, two mathematics books and one physics book. If they are randomly placed on the same shelf, the probability that the books of the same subject are not adjacent is () A. 15B. 25C. 35D. 45

There are five different books, including two Chinese books, two mathematics books and one physics book. If they are randomly placed on the same shelf, the probability that the books of the same subject are not adjacent is () A. 15B. 25C. 35D. 45

According to the meaning of the topic, we know that the topic is the probability of an equal possible event. The event involved in the experiment is that five books are randomly placed on a bookshelf, with a total of A55 = 120 results

For example: Mathematics Compulsory 1

There are five compulsory mathematics books and two optional ones
There are two compulsory and three optional physics books
There are two compulsory and three optional courses in chemistry
There are three compulsory and three optional biology books
All of them are introduced on the website of pep

2010 edition of mathematics book, English book, physics book and chemistry book of Heze No.1 Middle School

Generally, the editions of these books are unchanged
English mathematics and physics are published by people's education press
Chemistry, Shandong science and Technology Press

From six different English books and five different mathematics books, the probability of taking any five books, at least two in English and two in mathematics, is 0

There are 11 books in total, five of them are optional, with a total of C ^ 5_ 11 = 462 methods
Among them, 2 English books and 3 mathematics books are selected from (C ^ 2)_ 6）X（C^3_ 5) = 15x10 = 150 kinds,
Get 3 English books and 2 math books. The method is (C ^ 3)_ 6）X（C^2_ 5) = 20X10 = 200 kinds,
So the probability is (200 + 150) / 462 = 175 / 231

Let f (x) be a monotone function over the domain R + and satisfy f (XY) = f (x) + F (y) if f (1 / 3) = 1. (1) find the value of F (1) (2) if f (x) = 2,
The value of X

(1).f(1×1)=f(1)+f(1)
f(1)=2f(1)
f(1)=0
(2) Because the function is monotonic in R, there are no multiple x values that make the function value 2, so x has only one numerical value
f(x)=2=1+1=f(1/3)+f(1/3)
x=1/3×1/3=1/9

For a natural number less than 200, the sum of digits is 5 in Quaternary, 8 in hex, and 9 in octal,
Don't enumerate, number theory. Okay, 150 points

ABC is an n-ary number
Then ABC = a + B + C (modn-1)
X = 5 (MOD3)
x=8(mod5)
x=9(mod7)
Then x = 23 (mod105) (the above = are congruence symbols)
X = 23 or 128
Only 23 of them meet the requirements of the test
23 is the solution

Let the random variable x = e ^ y obey the exponential distribution with parameter E. find the probability density function of the random variable y

Shilling y = LNX
F (y) = P {y ≤ y} = P {LNX ≤ y} = P {x ≤ e ^ y} = FX (e ^ y) = 1-e ^ (- e ^ (y + 1)) this is the distribution function of Y
f(y)=F`(y)=e^(y+1-e^(y+1))
Are you sure the parameter is e

How to use matlab to solve the integral of sin (n * x)

>> syms x n
>> int(sin(n*x),'x')
ans =
-1/n*cos(n*x)
>>

Is it right to say that the meaning of fractional multiplication is 2 / 5 of 3

The meaning of multiplication is to find a few simple operations of the same addend sum. The meaning of a number into a fraction is to find the number of fractions of the number. For example, 3 * 2 / 5 means 2 / 5 of 3. In further understanding, it means that 3 is divided into 5 parts averagely, which means that the number of such 2 parts is actually 2 / 5 3. However, it is not reasonable to say so, which means that this statement is wrong

For example, the area of the large parallelogram in the figure is 48 square centimeters, and a and B are the middle points of the upper and lower sides. Can you find out the area of the small parallelogram (shadow part) in the figure?

Connect CD, the area of shadow is 48 △ 2 = 24 (square centimeter); answer: the area of small parallelogram (shadow) is 24 square centimeter