Let a and B be rational numbers. Judge whether the following statements are correct and explain the reasons ① If a = - B, then | a | = | B| ② If | a | = | B |, then a = - B

Let a and B be rational numbers. Judge whether the following statements are correct and explain the reasons ① If a = - B, then | a | = | B| ② If | a | = | B |, then a = - B

① If a = - B, then | a | = | B|
Correct. A and B are opposite numbers, and their absolute values must be equal
② If | a | = | B |, then a = - B
If | - 5 | = | - 5 |, then - 5 ≠ 5

Write the inverse proposition of the proposition "if the product of two real numbers is rational, then both numbers are rational"

Inverse No: if these two real numbers are not rational numbers, then the product of these two numbers is not rational
Inverse: if the two real numbers are rational, then the product of the two numbers is rational
No: if the product of two real numbers is not rational, then both numbers are not rational

The equivalent proposition that a is not really contained in B?
1) For any x belongs to a, you x does not belong to B
2) The intersection of a and B is an empty set
3) B is not really included in a
4) There exists x belonging to a such that X does not belong to B
It could be multiple choice
thank

4)
You can draw figures and judge them
The range of B is relatively large, and a = / b

LIM (cos1 / √ x) ^ 2x (x - > infinity)

Obviously, when x tends to infinity, 1 / √ x tends to 0, that is, cos1 / √ x tends to 1, then ln (cos1 / √ x) tends to 0, and (cos1 / √ x) ^ 2x = e ^ [2x * ln (cos1 / √ x)] let 1 / √ x = t, then x = 1 / T & # 178; ln (cos1 / √ x) = ln (1 + cost-1) obviously, cost-1 tends to 0, then ln (1 + cost-1) is equivalent to cost-1 and then equivalent to

Solution equation: 15 (x + 15) = 12-13 (X-7)

The result is: 6 (x + 15) = 15-10 (X-7), 6x + 90 = 15-10x + 70, 16x = - 5, x = - 516

According to the rule: (1) 1536______ ，96，24，6．（2）2，5，10，13，26，29，______ ，______ ．（3）12，34，56，78，______ ，______ ，1314．

(1) (2) 29 × 2 = 58; 58 + 3 = 61; (3) 7 + 28 + 2 = 910; 9 + 210 + 2 = 1112

(1 / 2) given the function f (x) = SiNx + TaNx, the arithmetic sequence {an} with 27 items satisfies that an belongs to (- 90 ', 90'), and the tolerance D is not zero, if f (A1) + F（

f(x)=sinx+tanxan=a1+(n-1)df(a1)=sina1+tana1f(a2)=sin(a1+d)+tan(a1+d)f(a3)=sin(a1+2d)+tan(a1+3d)..f(a26)=sin(a1+25d)+tan(a1+25d)f(a27)=sin(a1+26d)+tan(a1+26d)f(a1)+f(a27)=sina1+sin(a1+26d)+tana1+tan(a1...

Finding the definite integral of [- 1 / 2,1 / 2] function √ (1-x ^ 2)

Let x = Sint t ∈ [- π / 6, π / 6] by trigonometric substitution
∫[-π/6,π/6](cost)²dt=∫[-π/6,π/6](1+cos2t)/2dt=π/6+(√3)/4

The first line 1, the second line 2, 3, 4, the third line 5, 6, 7, 8.9, the fourth line 10.11.12, 13, 14, 15
Which row, column and number should 2005 be in?

I think you missed a 16 in the fourth line
The rule of this arrangement is that each row has two more numbers than the previous row
The number is 13 5 7 9. Roughly calculate the square root of 2005, which is more than 44
Using Gauss's summation formula, (1 + 87) x44 / 2 = 1936
2005-1936=69
So 2005 has 69 numbers on line 45
Let's take it

If a is the smallest non-zero natural number, B is the largest two digit number, and C is 2 times of 7.5, then a + B + C =?
Help answer the following questions
The original bookstore has m books, and bought 70, now a total of () books
The number of a is x, the number of B is y, and the sum average of a and B is ()

a=1,b=99,c=7.5*2=15
a+b+c=115
The original bookstore has m books, and bought 70, now a total of (M + 70)
The sum of a and B is (x + y) / 2