How to do the tenth question? Question 11: How to do it?

Nine and one fifth.

90 5 = 18 (hours) 18 2 = 9 (hours).

9 + 1/5 = 9 and 1/5.

Suppose it meets after x hours.

5x+4x=90

x = 10 hours.

The answer is 7 prime numbers, also known as prime numbers, and there are infinite numbers. A natural number greater than 1 is not divisible by other natural numbers (prime numbers) except 1 and itself, in other words, the number has no other factors than 1 and itself; Otherwise, it is called a composite number. According to the fundamental theorem of arithmetic, every integer greater than 1 is either a prime number in itself, or it can be written as a product of a series of prime numbers; And if you don't take into account the order of these prime numbers in the product, then the written form is unique.

The smallest prime number is 2. A natural number with only two factors, 1 and its own two factors, is called a prime number (or prime number). (Such as:.)

From 2 1 = 2 and 2 2 = 1, we can see that the factor of 2 is only two divisors, 1 and itself 2, so 2 is a prime number. In opposition to this is the composite number: "In addition to the two factors of 1 and itself, there are other factors called composite numbers."

For example: 4 1 = 4, 4 2 = 2, 4 4 = 1, it is obvious that the factor of 4 is in addition to the two factors of 1 and its own 4, there is also a factor of 2, so 4 is a composite number. There are prime numbers within 100, and there are 25 prime numbers within 100.

Prime number formulas: 235711, 13917, 232937, 314147, 435359, 617167, 7383889, plus 7997.

B's speed is 1 5 slower than A's

Then B's velocity is 4 kilometers per hour, and the sum of the distances traveled by A and B per hour is.

4+5 9 km, when the sum of the distances traveled by A and B is 90 km, the two meet.

90 9 = 10 hours, so after 10 hours, the two meet.

B speed is 1 3 slower than A speed

That is, B speed A speed A speed 1 5

So the first speed is 5 and the second speed is 4

The time elapsed between the two is the same, and the time is x

i.e. 5x 4x 90 so x 10

That is, the two meet after 10 hours.

The speed of A is 5 kilometers, and the speed of B is 1 4 kilometers of A, and the distance between the two people is shortened by 5 + 4 = 9 kilometers every 1 hour, and 90 9 = 10 hours is the time for the two people to meet.

The correct answer is B. The thermochemical equation for the standard molar enthalpy of silver bromide that correctly represents the enthalpy of formation must meet the following conditions: The measurement coefficient of the product produced by the equation must be one molar of silver bromide, so c is excluded; The reactants must be elemental in the standard state, so a (bromine is liquid in the standard state) and d (anions and bromine ions in the solution, not elemental in the standard state).

Therefore, B is eligible.

First, let's discuss in sections:

1. When x 2-1<=1, the value range [-2,2] is obtained, and the value range of x 2 is [-1,1].

f(x 2-1)> f(x 2) i.e.:

x^2-1>x/2

2x^2+x-1>0

The value range of x is x<-1 2 or x>1

The final range of values of x is obtained from the value range [-2,-1 2)u(1,2].

2. When x 2-1>1, the value range (negative infinity, -2) u(2, positive infinity) is obtained, and the value range of x 2 is (negative infinity, -1) u(1, positive infinity).

Again: (1) When the value range is (negative infinity, -2), the value range of x 2 is (negative infinity, -1), f(x 2-1), > f(x 2), i.e.,

1/2)^(x^2-1-1)>x/2

The left is a positive number, the right is a negative number, and it is constant, so the range of values (negative infinity, -2) is the solution set;

2) When the value range is (2, positive infinity), the value range of x 2 is (1, positive infinity), f(x 2-1)> f(x 2), i.e.,

1/2)^(x^2-1-1)>(1/2)^(x/2-1)

i.e.: (1 2) (x 2-2) > (1 2) (x 2-1).

Because the base number 1 2<1

So there is: x 2-21 4 + root 17 4, and the final value range is an empty set.

Based on the above discussions, the final solution set is: [negative infinity, -1 2)u(1,2].

= >> last question is incomplete.