Xiao Fang read a book. On the first day, she read 25% of the whole book. On the second day, she read 7 pages less than 25 pages of the whole book. There are 35 pages left to read. How many pages are there in this book?

The total number of pages in this book: (35-7) / (1-25% - 25), = 28 / 720, = 80 (pages)

Lele read a fairy tale book. On the first day, she read 25% of the whole book. On the second day, she read 20% of the whole book. There are 88 pages left. How many pages are there in this fairy tale book?
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Explain, thank you

160 pages, assuming that the whole book has x pages, then x-0.25x-0.2x = 88

Given sin ^ x + cos ^ x = 2 / √ 3, then TaNx + cosx=

Sum difference product
Arcsin (radical (2 / 3)) - pi / 4 = 0.9553166181
pi-0.9553166181=2.186276036
0.9553166181-pi/4=0.1699184546
2.186276036-pi/4=1.400877873
X = 0.1699184546 + 2kpi or 1.400877873 + 2kpi
TaNx + cosx = Tan (0.1699184546) + cos (0.1699184546) = 1.1571435 or
tanx+cosx=tan(1.400877873)+cos(1.400877873)=5.997529135

Problems of linear equations of two variables (preferably with process)
1、2(m-1)=3(n+2),2(n+3)=3(1-m).
2、150×2%+x×30%=（150+x+y)×3%,150×5%+y×60%=（150+x+y）×6%

This is easier: 1. You can simplify it first
2m-2 = 3N + 6,2n + 6 = 3-3m, then divide into 6m-6 = 9N + 18,6m-6 = - 4n-12, and subtract to get 6m-6 = 9N + 18,6m-6 = - 4n-12
N = - 30 / 13, M = 7 / 13, that is to say, n is: 30 / 13 of negative, M is: 7 / 13
2. The simplification result is 0.3x + 3 = 0.03x + 0.03y + 4.5, 0.6y + 7.5 = 0.06x + 0.06y + 9
27x-3y = 150, - 6x + 54y = 150, the solution is x = 285 / 48, y = 165 / 48

Use the definition of derivative to find the derivative of the following function
（1） f(x)=x^2
(2) F (x) = x ^ 2 + ax + B (a, B are constants)

（x+dx）^2-x^2=2xdx+(dx)^2
(x + DX) ^ 2-x ^ 2 / DX = 2x + DX, when DX approaches 0
（x+dx）^2-x^2/dx=2x
f(x+dx)-f(x)=2xdx+(dx)^2+adx
f(x+dx)-f(x)/dx=2x+a+dx
When DX approaches 0
It is 2x + a

If the positive integers a, B, C satisfy that a of B = C of 9, the square of a + C of B + 9 = 4 of 9, A2 + B2 + C2 = 49, then B =, C=

Then the square of [(B + 9) (a + C)] is 4 / 9, the square of [(9a / C + 9) (a + C)] is 4 / 9, the square of [(9a / C + 9) (a + C)] is 4 / 9, the square of [(9a + 9C) (a + C)] is 4 / 9, the square of [9C] is 4 / 9, the square of C is 36, and C is 6. Substituting (1) into (1), 3A = 2B, B = 3 / 2a, so A2

Einstein's special theory of relativity holds that the mass of an object will change with its own speed

Increase

How to calculate 2x * 3x

6x²
The coefficients multiply, and so does X

The circumference of a rectangle is 26cm. If the length of the rectangle is reduced by 1cm and the width is increased by 2cm, it will become a square. If the length of the rectangle is xcm, the equation ()
A. x-1=（26-x）+2B. x-1=（13-x）+2C. x+1=（26-x）-2D. x+1=（13-x）-2

Let the length of the rectangle be xcm, then the width is (13-x) cm. According to the equivalent relation: the length of the rectangle - 1cm = the width of the rectangle + 2cm, the equation is: X-1 = (13-x) + 2, so choose B

The radius of the car wheel is 1.2m, and the running speed is 72km / s. assuming that the car does not slip with the ground, the following results can be obtained: 1;
1. The wheel radius of the vehicle is 1.2m and the driving speed is 72km / s. assuming that the vehicle does not skid with the ground, the following formula is obtained:
1. The angular velocity of the wheel in driving;
2. What is the rotational speed of the wheel during driving?
2 the acceleration of gravity on the earth's surface go = 9.8 m / S & sup2;, neglecting the influence of the earth's rotation, what is the difference between the acceleration of gravity g and go in the air with the height h = 1000 m above the ground? (the radius of the earth r = 6.37 × 10 of the sixth power m)

1. (1) according to the angular velocity W = V / R, W is equal to 16.7m/s
(2) According to w = 2 π n, where n is the rotational speed, so n equals w / 2 π n equals 2.66 rad / s
2. According to Mg = the square of GMM / R, so go = the square of GM / R, g = the square of GM / (R + H), where m is the mass of the earth
Speak very clearly, the specific results with their own data!

Xiao Fang read a book. On the first day, she read 25% of the whole book. On the second day, she read 7 pages less than 25 pages of the whole book. There are 35 pages left to read. How many pages are there in this book?