If equations 4x−3y＝k If x and y are equal in 2x + 3Y = 5, then K is equal to () A. 1 or - 1 B. 1 C. 5 D. -5

If equations 4x−3y＝k If x and y are equal in 2x + 3Y = 5, then K is equal to () A. 1 or - 1 B. 1 C. 5 D. -5

According to the meaning of the title:
4x−3y＝k(1)
2x+3y＝5(2)
x＝y(3) ，
Substituting (3) into (2) gives x = y = 1,
Substituting (1) gives k = 1
Therefore, B

If we know that the mean of 3,4,2x, 3Y is 6 and that of 3x, 2Y is 4, then x + y=

3+4+2x+3y=24
3x+2y=8
So 5x + 5Y = 25
x+y=5

It is known that the average of the four numbers 2,6, x, 2Y is 4 and the average of 5,10,2x, 3Y is 8. Find the values of X and y

because
The average of 2,6, x, 2Y is 4
therefore
2+6+x+2y=4*4=16
x+2y=8
And the average of 5, 10, 2x, 3Y is 8,
5+10+2x+3y=8*4=32
2x+3y=17
therefore
x=10,y=-1

It is known that the system of equations {① 2x + ay = B ② x + 2Y = 3, when a ≠ (), the system of equations has unique solution; when a = () and B = (), there are innumerable equations When a = (), B ≠ (), the system of equations has no solution

2x+ay=b ⑴
x+2y=3 ⑵
(2) × 2 - 1
(4-a)y=6-b
Observe the equation
When a is not equal to 4, the system of equations has a unique solution
When a is equal to 4 and B = 6, the system of equations has innumerable solutions
When a is equal to 4 and B is not equal to 6, the system of equations has no solution

In the system of equations about X, y 2x+y＝1−m In X + 2Y = 2, if the unknown number x, y satisfies x + Y > 0, then the value range of M is () A. m＜3 B. m＞3 C. m≥3 D. m≤3

2x+y＝1−m①
x+2y＝2      ② ，
① + 2: 3 (x + y) = 3-m, that is, x + y = 3 − M
3，
Substituting x + Y > 0 leads to 3 − M
3＞0，
The solution is: m < 3
Therefore, a

We know that the unknown numbers x and y of the equations 2x + y = 1-m, x + 2Y = 3 satisfy X-Y > 0, and find the value range of M

set up
X-Y
=a(2x+y)+b(x+2y)
=2ax+ay+bx+2by
=(2a+b)x+(a+2b)y
Then there are
2a+b=1 1
a+2b=-1 2
1 + 2
a+b=0 3
1-3
A=1
2-3
b=-1
therefore
X-Y
=(2x+y)-(x+2y)
=1-m-3>0
M

In the system of equations about X, y 2x+y＝1−m In X + 2Y = 2, if the unknown number x, y satisfies x + Y > 0, then the value range of M is () A. m＜3 B. m＞3 C. m≥3 D. m≤3

2x+y＝1−m①
x+2y＝2      ② ，
① + 2: 3 (x + y) = 3-m, that is, x + y = 3 − M
3，
Substituting x + Y > 0 leads to 3 − M
3＞0，
The solution is: m < 3
Therefore, a

In the system of equations 2x−y＝m In 2Y − x = 1, if x and y satisfy x + Y > 0, then the value range of M is () A. B. C. D.

By adding the two equations,
x+y=1+m，
And ∵ x + Y > 0,
∴1+m＞0，
M ＞ - 1 is obtained by moving the term;
Since the solution set does not contain - 1,
So choose B

Given that the average of the four numbers 2, 7, x, 3Y is 4.5, and that of 7, Y-3, 7-2x, x-2y is 2, then X-Y is equal to______ .

The average of the four numbers is 4.5; and the average of the four numbers is 4.5; and the average of the four numbers is 4.5; and the average of 2 + 7 + X + 3Y = 4.5 × 4 = 18, ∵ x + 3Y = 9, ∵ 7, Y-3, 7-2x, x-2y, x-2y is 2, the average of the four numbers is 2, Ɂ 7 + Y-3 + 7-2x + x-2y = 2 × 4 + Y-3 + 7-2x + x-2y = 2 × 4 ɂ X-Y = 3, \y = 9x + 3Y = 9x + y = 3, x = 0y = 3, x = 0y = 3, X = 0y = 3 = 3 = - 3

We know that the average of 4,6,3x, 2Y is 8; the average of 8,9,2x, 3Y is 10. Find the value of X, y

(4+6+3x+2y)/4=8
(8+9+2x+3y)/4=10
Find x = 4, y = 5