There are 200 science and technology books in the school library, accounting for 2 / 5 of the total number of books. How many other books are there in the school library

There are 200 science and technology books in the school library, accounting for 2 / 5 of the total number of books. How many other books are there in the school library

Hello! I'm glad to have 200 science and technology books in the library, accounting for 2 / 5 of the total number of books. Then the total number of books is: 200 ^ (2 / 5) = 500 (Books). Other books are: 500-200 = 300 (Books). The formula is: 200 ^ (2 / 5) - 200 = 300 (Books). Answer: there are 300 other books in the school library

Why does the author think of the little girl who spent the summer camp in Qingdao in front of Peking University Library?
The problem of 13-year-old's fortune,

A: because when the author knows that there are more than 4 million books in the library of Peking University, and what he spent in it is not satisfied with the smallest fraction of this number, he feels his ignorance. That's why he thinks of the little girl who sobs because of her ignorance

Square ABCD, ab = 6, e is any point on the edge of AB, f is any point on the edge of AD. EF = 5, angle EFC = 45 degrees
Square ABCD, ab = 6, e is any point on AB side, f is any point on ad side. EF = 5, angle EFC = 45 degrees,

Extend FD to point G so that DG = be
Then △ CDG ≌ △ CBE
∴CE=CG,∠BCE=∠GCD
∵∠BCD=90°,j5ECF =45°
∴∠FCG=∠∠FCD+∠GCD=∠FCD+∠BAE=45°
∴∠ECF=∠FCG
∵CF=CF
∴△ECF≌△GCF
∴FG=5
∴S△ECF=S△FCG=1/2*5*6=15

It is known that propositions P: X1 and X2 are two real root inequalities of the equation x ^ 2-mx-2 = 0, a ^ 2-4a-2 > = lx1-x2l
It is known that propositions P: X1 and X2 are two real roots of equation x ^ 2-mx-2 = 0, inequality a ^ 2-4a-2 ≥ lx1-x2l holds for any real number m [- 1,1]; proposition q: only one real number x satisfies inequality x ^ 2 + 2 √ 2aX + 11a ≤ 0, if proposition p is a false proposition, proposition q is a true proposition, and the value range of a is obtained

X1 and X2 are the real roots of the equation x ^ 2-mx-2 = 0,
∴|x1-x2|=√(m^2+8),
The inequality a ^ 2-4a-2 ≥ | x1-x2 | holds for any real number m, which belongs to [- 1,1],
a^2-4a-2≥3,
A ^ 2-4a-5 > = 0, a > = 5 or a

A = (1,0,2) B = (0,2,1) try to determine the normal vector of the plane

a. B. cross product
Because the vector obtained by cross multiplication of a and B is perpendicular to a and B
It is the normal vector of the plane containing a and B
The solution is as follows
i,j,k
1,0,2
0,2,1
=(0*1-2*2)i-(1*1-0*2)j+(1*2-0*2)k
=-4i-j+2k
That is, the normal plane vector is (- 4, - 1,2)

Multiplication of polynomials
[(11x + 2) · (2 * 120) - 120 square] + [3.14 * (60 + x) square △ 2-3.14 * 60 square △ 2]=

2640*x-19572+1.57*(60-x)^2

In the cube ABCD-A ` B ` c ` d ', e and F are the middle points of edge AA'. CC ', respectively. Then there are several lines intersecting with three lines a ` d', EF and Cd in space

Countless lines: let p be any point on DC. P and a & # 39; D & # 39; can determine the plane α. & nbsp; α and EF must have intersection Q (note that E.F is on the opposite side of α). On α, the extension of PQ must intersect the straight line a & # 39; D & # 39; (see Figure), ∵ P is arbitrary, and there are countless PQS

One tenth of the power of 2008 multiplied by three and one third of the power of 2007 =?

(-1/10)^2008×(10/3)^2007
=(-1/10)^2007×(10/3)^2007×(-1/10)
=(-1/10×10/3)^2007×(-0.1)
=((1/3)^2007×0.1
=1/(10×3^2007)

As shown in the figure, M is the midpoint of AB and P is any point on BM. The formula shows that (1) if PM = 1 / 3PB and Pb = 6, find the length of ab

Solution
∵ m is the midpoint of ab
∴AM＝BM＝AB/2
∵PM＝PB/3,PB＝6
∴PM＝6/3＝2
∴BM＝BP+PM＝6+2＝8
∴AB＝2BM＝16

How to solve a problem with two XS? For example: 3x out of 4-5x out of 5 = 11 out of 12

3x/4-x/5=11/12
（3/4-1/5）x=11/12
Divide the general part in brackets:
（15/20-4/20）x=11/12
11/20x=11/12
∴x=5/3