Matlab a is a matrix, B is a matrix A=[-1 2 4;3 -1 1;2 1 4;] B=ones(2,2) A(B)= -1 -1 -1 -1 Why?

Matlab a is a matrix, B is a matrix A=[-1 2 4;3 -1 1;2 1 4;] B=ones(2,2) A(B)= -1 -1 -1 -1 Why?

If x and y are vectors, then x (y) is a vector as long as y, and the ith element of X (y) is x (Y (I))
Similarly, if the subscript b is not a vector but a matrix, then a (b) is a matrix as large as B, and the (I, J) element of a (b) is a (b (I, J))
Of course, it also involves the meaning of a (I) when a is a matrix. Just pull a into a vector by column to understand it

How does matlab define a matrix of prescribed form
We need to define a matrix. The n * n matrix simulates a square plate with side length L. there is a hole with radius r in the center of the plate, so the value of the matrix element is: the hole is 1 and the edge is 0. How to write?

Use two for loops to search the row and column, and then assign the value inside the garden to 1, and the value outside the garden to 0. The judgment condition is the radius formula of the garden

How to write the regular form of math problem 9-1 = 9,16-4 = 12,25-9 = 16 in Grade 7

（n+2)^2-n^2=4n+4
I mean square by ^ 2

It is known that the inverse scale function y = K / X is related to the image and a point (- 1,2) of the linear function y = MX + N, and the distance between the image of the linear function and the x-axis focus to the origin is 3
Inverse proportion function and a function expression for the goddess of mathematics male gods to help

Because (- 1,2) is on the image of y = K / x, so k = - 2.. so the analytic expression of the inverse scale function is y = - 2 / X. because the distance from the intersection of y = MX + N and X axis to the origin is 3, the image of y = MX + n passes through (3,0) or (- 3,0). When (- 1,2), (3,0) is on y = MX + N, there is 3M + n = 0, - M + n = 2, the solution is: M =

A cylindrical reservoir with a bottom radius of 10 meters can store 1570 cubic meters of water. If the depth of excavation is 5 meters, how many cubic meters can the reservoir store?

Bottom area = 3.14 * 10 * 10 = 314 square meters 1570 + 314 * 2.5 = 1655 cubic meters

Calculating 24 points: 3,4, - 6,10 requires three algorithms. 3, - 5,7, - 13 requires one algorithm

3,4, - 6,10 is 24 points, 3 x [10 + 4 + (- 6)] = 2410 - 3 x (- 6) - 4 = 24-64 - 10 x (- ---) = 2433, - 5,7, - 13 is 24 points (- 5) x (- 13) + 7 -------- = 243, I'll give you another question, 3,3,8,8 is 24 points, I hope my answer will help you

Find the extremum point and monotone interval of function y = 2x ^ 3-15x ^ 2 + 36x-27 (find process!)

Y '= 6x ^ 2-30x + 36 = 6 (x ^ 2-5x + 6) = 6 (X-2) (x-3) = 0, the extreme point is x = 2,3
F (2) = 16-60 + 72-27 = 1 is the maximum point
F (3) = 54-135 + 108-27 = 0 is the minimum point
Monotone increasing interval: x3
Monotone decreasing interval: 2

4500 ml equals () cubic centimeter. 0.086 cubic decimeter equals () liter

4500 ml equals (4500) cubic centimeter and 0.086 cubic decimeter equals (0.086) liter

If the front view and the left view of a three view simple space geometry are equilateral triangles with side length of 2, and the top view outline is a square, then its volume is___ ．

As shown in the figure, according to the conditions, the geometry is a square with the bottom side length of 2, the side is an isosceles triangle, and the height of the bottom side is also an equilateral pyramid of 2, so its volume v = 13 × 4 × 22-1 = 433

The symmetry axis of the parabola y = (K Λ 2-2) x Λ 2 + m-4kx is a straight line x = 2, and its lowest point is on the straight line y = - 0.5x + 2. The analytic expression of the function is obtained
The symmetry axis of parabola y = (K Λ 2-2) x Λ 2 + m-4kx is a straight line x = 2, and its lowest point is in the straight line
On y = - 0.5x + 2, find the analytic expression of the function

For y = (k ^ 2-2) x ^ 2 - 4kx + M
Because the axis of symmetry is a straight line, x = 2
4K / 2 (k ^ 2-2) = 2, and K ^ 2-2 > 0
The solution is: k = 2 (k = - 1, rounding off)
Therefore, the parabola is y = 2x ^ 2-8x + M
According to the analysis, the lowest point of parabola is as follows:
x=2；
Y=-0.5x+2
I.e. (2,1)
Take this point into the parabola:
1=2*2^2-8*2+m
→m=9
Therefore, the analytic expression of the function is
Y=2x^2-8x+9