How to calculate 7 / 6 * 5 / 9 + 4 / 9 * 5 / 6

7/6*5/9+4/9*5/6
=5/6*7/9+4/9*5/6
=5/6*(7/9+4/9)
=5/6*11/9
=55/54

The power of rational number: what is the square of 3?, - 3? How many is the square of 9? Is there a rational number whose square is - 9? Hurry, please

Is the square of 3 the square of 9-3 or the square of 9? Only two squares without any number are negative

As shown in the figure, a factory is connected with a and B by road and railway. The factory purchased a batch of raw materials of 1000 yuan per ton from a to transport them back to the factory, and made products of 8000 yuan per ton to B. the road freight rate is 1.5 yuan / (t · km), and the railway freight rate is 1.2 yuan / (t · km). The total cost of the two transportation is 15000 yuan by road and 97200 yuan by railway How much more than the sum of raw material cost and transportation cost? The black and white lines in the picture represent railways and the other lines represent highways

Suppose that the factory purchased x tons of raw materials from a and transported y tons of products to B. according to the meaning of the title, we get 15x + 30y = 15000144x + 132y = 97200, and the solution is: x = 400Y = 300. Therefore, the sales cost of this batch of products is more than the sum of raw material cost and transportation cost: 300 × 8000-400 × 1000-15000-97200 = 1887800 (

To solve the mathematical problem of unknown number:
1: A number is 115 larger than 20% of 205. What's the number?
2: The number a is 36. 50% of the number a is equal to 40% of the number B

1.205*20%+115=156
2. Let B be x 36 * 50% = x * 40% x = 45

Let f (a) = sin ^ x α + cos ^ x α, X ∈ {n | n = 2K, K ∈ n +}
Using trigonometric transformation, we estimate the value of F (α) when x = 2,4,6, and make a conjecture about the value range of F (α) when x is a general value
Senior one mathematics trigonometric identity transformation in the question, compulsory 4 P144 fifth question, online and other answers

When α = 2, sin ^ 2 α + cos ^ 2 α = 1. When α = 2, sin ^ 4 α + cos ^ 4 α = (sin ^ 2 α + cos ^ α) ^ 2-2sin ^ 2 α cos ^ 2 α = 1-1 / 2 (sin ^ 2 α) ^ 2, so 1 / 2 ≤ sin ^ 4 α + cos ^ 4 α ≤ 1 sin ^ 6 α + cos ^ 6 α = (sin ^ 2 α + cos ^ 2 α) (sin ^ 4 α - Sin ^ 2 α cos ^ 2 + cos ^ 4 α) = (sin ^ 2 α) = (sin ^ 4 α - Sin ^ 2 α cos ^ 2 + cos ^ 4 α) = (sin ^ 2 α)

The number of 2008 digits composed of 2008 2 is 2222 ~} the remainder of 2008 2 divided by 13 is?

The number of six two, 222222 △ 13 = 17094
2008 ÷ 6 = 334 more than 4, that is, the number of 2 in 2008 contains 334 222222, and there are still 4 2
The number of 4 2, 2222 △ 13 = 170, more than 12
Then, the number of 2008 digits composed of two in 2008 is
2222…… two thousand two hundred and twenty-two
=2222+222222×(10^4+10^10+10^16+…… +10^2002)
=12+13×170+13×17094×(10^4+10^10+10^16+…… +10^2002)
So:
The number of 2008 digits made up of two in 2008 is 2222 The remainder of 2222 divided by 13 is 12

1.3 / 13-2 / 5 + 10 / 13-3 / 5 2.2/7 divided by [3 / 7X (2 / 3 + 7 / 9)] (/ is a fractional line) (simple operation)
Simple operation

1.3/13-2/5+10/13-3/5
=(3+10)/13-(2+3)/5
=1-1
=0
2 / 7 divided by [3 / 7X (2 / 3 + 7 / 9)]
=(2 / 7) divided by [3 / 7X (6 / 9 + 7 / 9)]
=(2 / 7) divided by [3 / 7X (13 / 9)]
=(2 / 7) divided by [13 / 21]
=(2x21)/(7x13)
=6/13

Solving differential equation by undetermined coefficient method
Is the undetermined coefficient method the same as the constant variation method? What's the form of Y *? I can't find it in the book. I've been asking for advice

In some special cases, the undetermined coefficient method is more convenient to solve the n-order linear non-homogeneous differential equation with constant coefficients. There are some classifications in the book: 1. If the non-homogeneous part is p (x) e ^ ax, the corresponding value of the non-homogeneous part is not the eigenvalue, then the special solution is (AX ^ m + BX ^ M-1...) e ^ ax if it is the eigenvalue (k-fold

How many cubic meters is a ton of water equal to?

1t water is 1000kg, the density of water is 1000kg / m3, so it is exactly 1m3

How to calculate 7 / 6 * 5 / 9 + 4 / 9 * 5 / 6