The problem of matrix multiplication AB=0 Is ab a zero matrix, or is the determinant of AB zero?

The problem of matrix multiplication AB=0 Is ab a zero matrix, or is the determinant of AB zero?

Zero matrix

Circle and equation (15 17:18:39)
Find the center of the circle on the straight line X-Y-4 = 0, and take the common chord of two circles x2 + y2-4-6x = 0 and X2 + y2-4y-6 = 0 as the square of the first circle

Simultaneous equations x2 + y2-4-6x = 0 and X2 + y2-4y-6 = 0
Two solutions K1 and K2 are obtained
The circular equation is solved by using the equal distance between the point on the straight line X-Y-4 = 0 and the two points K1 and K2 (the distance formula from point to point)

Fill in the brackets to make the equation true
() 99999 () divided by 9 = 222222
() 99999 () divided by 9 = 333333
() 99999 () divided by 9 = 444444
() 99999 () divided by 9 = 555555
() 99999 () divided by 9 = 666666
() 99999 () divided by 9 = 777777

(1) 99999 (8) divided by 9 = 222222
(2) 99999 (7) divided by 9 = 333333
(3) 99999 (6) divided by 9 = 444444
(4) 99999 (5) divided by 9 = 555555
(5) 99999 (4) divided by 9 = 666666
(6) 99999 (3) divided by 9 = 777777

If the solution of the binary linear equations {3x ay = 16,2x + by = 15} about X and Y is {x = 7, y = 1, then what are the solutions of the equations {3 (x + y) - A (X-Y) = 16,2 (x + y) + B (X-Y) = 15 about X and y? What are the skills in solving this problem? Try to analyze and solve them according to the characteristics of the two equations

The solution of {3x ay = 16,2x + by = 15 is {x = 7, y = 1,
Then,
21-a = 16, a = 5
14 + B = 15. The solution is b = 1
A = 5, B = 1
｛3（X+Y）－A(X－Y)=16,2（X+Y）+B(X－Y)=15
Then,
3（X+Y）－5(X－Y)=16
2（X+Y）+(X－Y)=15
The solution of simultaneous equations is x = 4, y = 3

Simplify 2sin130 + sin100 (1 + √ 3tan370)

1+√3tan370
=2(1/2+√3/2tan10)
=2(sin30+cos30(sin10/cos10))
=2sin40/cos10
So the original formula = 2cos40 + cos10 (2sin40 / cos10)
=2(sin40+cos40)

List the equation, and find the solution of the equation, a number of 5 times plus the product of 4 and 5, the sum is 80, find this number

Let's solve the number four X
5x+4×5=80
5x+20=80
5x=60
x=12

On Xiaojun's birthday, the cake was divided into 10 parts. Xiaohong ate 4 pieces, Xiaoming 4 pieces, Xiaofang 2 / 10 and Xiaojun 3 / 10
Xiao Jun ate some cakes, Xiao Ming ate some cakes

10 * 2 / 10 = 2 (pieces) a: Xiaofang ate 2 pieces
10 * 3 / 10 = 3 (yuan) a: Xiaojun ate 3 yuan

In the plane rectangular coordinate system, a (0,1) B (2,0) C (2,3) (1) finds the area of triangle ABC (2) if there is a point P in the second quadrant

(1) Because B (2,0) C (2,3)
So edge BC / / X axis, and the distance between BC and X axis is 2
If ad is high on the edge of BC, then IADI = 2
From B (2,0) C (2,3), we can see that ibci = 3
So the area of triangle ABC = 1 / 2 * 3 * 2
＝3.
(2) As the question is not clear, it cannot be answered

How many hours is nine minutes

9/60=0.15
0.15 hours

The equation for finding the line L parallel to the line 3x + 4Y + 1 = 0 and the sum of intercept on two coordinate axes is 7 / 3

Let the equation of line l be y = (- 3 / 4) x + B. when x = 0, y = B. when y = 0, x = (4 / 3) * B
∵ the sum of intercept of line L on two coordinate axes is 7 / 3, ∵ B + (4 / 3) * b = 7 / 3, ∵ B = 1
The line L is y = (- 3 / 4) x + 1