Please explain the meaning of the following sentence and give a specific example: elementary row transformation is equivalent to multiplying a matrix left by an invertible matrix

Please explain the meaning of the following sentence and give a specific example: elementary row transformation is equivalent to multiplying a matrix left by an invertible matrix

It is to do elementary row transformation on the matrix, which is equivalent to multiplying the matrix left by an invertible matrix
for example
The matrix (x1, Y1; X2, Y2) changes two rows into (X2, Y2; x1, Y1)
Equivalent to (0,1; 1,0) * (x1, Y1; X2, Y2) = (X2, Y2; x1, Y1)

Given the adjoint matrix A * = diag (1,1,1,8) of matrix A, why can we deduce a = 2 from a * 8

|A*| = |A|^(n-1) = |A|^3 = 8
So | a | = 2

Does the sign of a matrix change after a newline?

Matrix newline is the elementary line transformation of matrix without changing the symbol

How to calculate 4 × 0.15 + 0.15 × 2.6) × 3?

[0.15×（17.4+2.6）]×3
=（0.15×20）×3
=3×3
=9

When k, m take______ Then the equations y = KX + my = (2k − 1) x + 4 have at least one solution

When k = 2k-1, M = 4, the line y = KX + m coincides with the line y = (2k-1) x + 4, that is, the system of equations has innumerable solutions, so k = 1, M = 4; when k ≠ 2k-1, M = 4, the line y = KX + m has an intersection with the line y = (2k-1) x + 4, that is, the system of equations has one solution, so K ≠ 1, M = 4

I need the first grade volume 2 math problems

A rectangular cardboard, along its length and width minus a 2.5cm wide small strip of paper, area than the original area reduced by 28 square centimeters, the original perimeter of this cardboard is______ Cm

(28.5 △ 2.5 + 2.5) × 2, = (11.2 + 2.5) × 2, = 13.7 × 2, = 27.4 (CM), answer: the original perimeter of rectangular paperboard is 27.4 cm

It is known that the sinusoidal AC current I = 10sin {314T_ 90 degrees} a seek maximum effective value frequency period initial phase urgent! Urgent!

10 10/（√2） 0.5 2 -π/2
I'm taking an exam now. Ha ha, I've passed the exam

Known rectangular paper length of 80 cm, cut from the largest square, the remaining rectangular circumference is how many cm

Let the width of the rectangle be x, then the side length of the subtracted square is also x, and the perimeter of the remaining rectangle is X
2x+2*(80-x)=160

How is pulse and heartbeat produced

There are sinoatrial node and atrioventricular node in the heart. Sinoatrial node is located at the junction of superior vena cava and right atrium. The deep surface of epicardium in the upper segment of the boundary groove is the normal pacing point of the heart. Atrioventricular node is the most important secondary pacing point, and it is the incidence area of many arrhythmias. Heart beating causes blood flow, and ejects from the heart into the artery, which can be felt on the body surface, that is, pulse