1. There are three Chinese books and five mathematics books in the books. We should ensure that we can take out two Chinese books at a time, at least how many books? 2. There are five pencils of three colors and the same shape in one box. How many pencils can be taken at one time to ensure one of each pen?

1, 7 (the worst case is that the first five times I took a math book)
5+2=7
2,11 (the worst case is that the first five pens are of the same color, and the sixth to tenth pens are of the same color) 5 + 5 + 1 = 11

There are five different books, including two Chinese books, two mathematics books and one physics book. If they are randomly placed side by side on the same shelf, the probability that the books of the same subject are not adjacent is very high

12 divided by 30 is two fifths

-__________________ A simple physics conversion problem
The energy released by a big earthquake is amazing. The energy released by a magnitude 7 earthquake is about the 16th power of 1.98x10, which is equivalent to the work of a 1 million kilowatt power station In my opinion, this question is not too difficult, but the answer is not consistent with the answer. I doubt that my calculation method is wrong. Please, elder martial sisters and elder martial brothers,
Sorry, there was a mistake in the question just now. The energy released is the 16th power of 1.98 * 10, and the unit is Joule.

1KWH=3.6*10^6 J
1.98*10^16/3.6*10^6=5.5*10^9 KWH
One million kilowatt power station generates electricity every day:
24*10^6=2.4*10^7 KWH
5.5 * 10 ^ 9 / 2.4 * 10 ^ 7 = 2.29 * 10 ^ 2 days = 229 days

How to find Pi? Method, do not approximate, it is best to hundreds of numbers

That is circumference △ diameter length = circumference ratio
thank you

Find the plane equation parallel to the plane 6x + y + 6Z + 5 = 0 and the volume of tetrahedron enclosed by three coordinate planes is one unit
Ask for detailed explanation

Let the plane equation be 6x + y + 6Z = P, and the coordinates of the intersection point with the coordinate axis be (P / 6,0,0), (0, P, 0), (0,0, P / 6)
Then 1 / 6 * P ^ 3 / 36 = 1, P = 6

Let f (x) = x power of a pass through point (2,9) and find f (- 1)

f(x)=a^x
Passing point (2,9)
9=a^2
a=3 or -3
f(-1)=1/3 or -1/3

Both 6 and 4 can be divided by 8 () a
B. Divisibility

6 △ 8 = 0.75; 4 △ 8 = 0.5; both 6 and 4 can be divided by 8

Ellipse x ^ 2 / A ^ 2 + y ^ 2 / b ^ 2 = 1, F1F2 as the focus, P on the ellipse, if the angle f1pf2 = 60 degrees, find the range of E

When B is at the vertex of the minor axis
Angle f1bf2 Max
therefore
sixty

The product of two prime numbers is 34 and 19. What are the two prime numbers? What is the total sum?

2 and 17

If the function image is symmetric with respect to two straight lines X = a, x = B, then is the function y = f (x) a periodic function

f(a+x)=f(a-x)
F (B + x) = f (b-X) satisfies
a+x=t
f(b-a+a+x)=f(b-a+t)=f(b-(t-a))=f(b+a-t)
f(t)=f(2a-t)
If B-A is its period, then f (B + A-T) = f (2a-t), that is, a = B, but a and B are not necessarily equal, so it is not necessarily a periodic function