What is the product of Two Elementary Matrices?

What is the product of Two Elementary Matrices?

Elementary matrix is a kind of simple and special matrix, and its function is also "simple". For example, if the elementary matrix is left multiplied by a matrix A (a can be any matrix), then the result of multiplication is: the elementary matrix implements the elementary row transformation operation on matrix A (refer to the book for the specific elementary transformation)

Input a matrix of m x n and a matrix of N x m, and then find the product of the two matrices

The i-th row and j-th column of the new matrix are equal to the sum of the products of the i-th row of the first matrix and the j-th column of the second matrix

As shown in the figure, place the small room with chess pieces, the first 5, the second 11, the third 17, ask the nth

6n-1

Mathematical elementary third quadratic function and geometric maximum value problem
Make a rectangle ABCD in a right triangle, where AB and AD are on two right sides respectively. If the right side where AB is located is 8 and ad is located is 6, then the functional relationship between the rectangle area y and the length x of AB side is and the maximum value of Y
This question should be C point is not necessarily in AC, then how to make it, do not understand, request detailed explanation, urgent
The data on the first floor are not quite right

Let ad = Z
z/30=（40-x）/40
z=30-3/4*x
y=z*x=（30-3/4*x）*x=-3/4*x^2+30x
When x = - B / 2A = 30 / (3 / 2) = 20, take the maximum value
Maximum y = 300

It is known that the function f (x) = (the square of PX + 2) divided by (q-3x) is odd, and f (2) = 5 / 3
(1) Finding the analytic expression of function f (x)
(2) The monotonicity of function f (x) on (0,1) is judged and proved

（1）
Because the function f (x) = (the power of PX + 2) divided by (q-3x) is odd
And because the square of PX + 2 is even
So q-3x is an odd function
So q = 0
And because f (2) = 5 / 3
Substituting P = 2
The analytic expression of function f (x): the square of 2x + 2) divided by (- 3x)
（2）
Because on (0,1), x + X decreases by one tenth
So f (x) = (- 2 / 3) * (x + 1 / x) increases monotonically

If the real number AB satisfies A2 + B2 + 3AB = 1, find a + B

Let a + B = M
a²+b²+3ab=(a+b)²+ab=1
Then, ab = 1 - (a + b) &# 178; = 1-m & # 178;
A and B are two real roots of the equation x & # 178; - MX + (1-m & # 178;) = 0,
△=m² - 4(1-m²) = 5m² - 4 ≥0
The solution is m ≥ 2 √ 5 / 5 or m ≤ - 2 √ 5 / 5
A + B ≥ 2 √ 5 / 5 or a + B ≤ - 2 √ 5 / 5

In the triangle ABC, ad = half DC, EC = one third EB

Connecting AE, because EC = EB / 3, that is, EC = BC / 4, so s △ AEC = s △ ABC / 4, and s △ Dec = s △ AEC * 2 / 3
So there is s △ Dec = s △ ABC / 6, so the area ratio of part a and part B is 5:1

How many square meters and decimeters is one square kilometer

Answer: 1 square kilometer = 1 000 000 square meter = 100 000 square decimeter

As shown in the figure, the area of the shadow part is 30 square centimeters, and the area of the trapezoid is calculated

(6 + 10) × (30 × 2 ／ 10) ／ 2 = 16 × 6 ／ 2 = 96 ／ 2 = 48 (square centimeter). Answer: the area of trapezoid is 48 square centimeter

If the perimeter of the triangle is 56 cm, the perimeter of the triangle composed of its three median lines is ()
A. 18cmB. 28cmC. 24cmD. 36cm

According to the line segment connecting the middle points of the two sides of the triangle is called the median line of the triangle, and the median line of the triangle is equal to half of the third side, then the perimeter of the triangle composed of its three median lines is half of the perimeter of the original triangle, that is 28cm