Question

Алгебра 7 клас
Знайдіть розв’язок системи рівнянь:

1) 4х+у=12
7х+2у=20

2) х-2у=5
3х+8у=1

3) 4у-х=11
5х-2у=17

4) 6х-у=-1
2х-3у=-11

5) х+у=7
9у-2х=-25

6) 5х-3у=0
15х+2у=55.

Answer 1

Ответ:

1)7x + 2(12 - 4x) = 20

7x + 24 - 8x = 20

-x = -4

x = 4

4(4) + y = 12

4(4) + y = 12y = 12 - 16

4(4) + y = 12y = 12 - 16y = -4

(x, y) = (4, -4)

2)3(5 + 2y) + 8y = 1

3(5 + 2y) + 8y = 115 + 6y + 8y = 1

3(5 + 2y) + 8y = 115 + 6y + 8y = 114y = -14

3(5 + 2y) + 8y = 115 + 6y + 8y = 114y = -14y = -1

x - 2(-1) = 5

x - 2(-1) = 5x + 2 = 5

x - 2(-1) = 5x + 2 = 5x = 3

(x, y) = (3, -1)

3)5(4y - 11) - 2y = 17

5(4y - 11) - 2y = 1720y - 55 - 2y = 17

5(4y - 11) - 2y = 1720y - 55 - 2y = 1718y = 72

5(4y - 11) - 2y = 1720y - 55 - 2y = 1718y = 72y = 4

4(4) - x = 11

4(4) - x = 1116 - x = 11

4(4) - x = 1116 - x = 11x = 5

(x, y) = (5, 4)

4)2x - 3(6x + 1) = -11

2x - 3(6x + 1) = -112x - 18x - 3 = -11

2x - 3(6x + 1) = -112x - 18x - 3 = -11-16x = 8

2x - 3(6x + 1) = -112x - 18x - 3 = -11-16x = 8x = -0.5

6(-0.5) - y = -1

6(-0.5) - y = -1-3 - y = -1

6(-0.5) - y = -1-3 - y = -1y = 2

(x, y) = (-0.5, 2)

5)9y - 2(7 - y) = -25

9y - 2(7 - y) = -259y - 14 + 2y = -25

9y - 2(7 - y) = -259y - 14 + 2y = -2511y = -11

9y - 2(7 - y) = -259y - 14 + 2y = -2511y = -11y = -1

x + (-1) = 7

x + (-1) = 7x = 8

(x, y) = (8, -1)

6)15x + 2(5/3)x = 55

15x + 2(5/3)x = 5515x + (10/3)x = 55

15x + 2(5/3)x = 5515x + (10/3)x = 5545x + 10x = 165

15x + 2(5/3)x = 5515x + (10/3)x = 5545x + 10x = 16555x = 165

15x + 2(5/3)x = 5515x + (10/3)x = 5545x + 10x = 16555x = 165x = 3

5(3) - 3y = 0

5(3) - 3y = 015 = 3y

5(3) - 3y = 015 = 3yy = 5

(x, y) = (3, 5)

Объяснение:

:)