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anzhelika [568]
3 years ago
7

Please answer quickly.

Mathematics
1 answer:
vladimir2022 [97]3 years ago
3 0

Answer:

1. B. (9, 4)

2. D. (2, -7)

3. C. (20, 30)

4. C. (3/4, -1/5)

Step-by-step explanation:

1.

Eq.1      3x – 5y = 7     Multiply by -2.

Eq. 2    2x + 3y = 30    Multiply by 3.

Eq. 1 becomes: -6x + 10y = -14

Eq. 2 becomes: 6x + 9y = 90

Add the two new equations to get:

19y = 76

y = 4

Now substitute 4 for y in the first original equation and solve for x.

3x - 5(4) = 7

3x -20 = 7

3x = 27

x = 9

Answer: (9, 4)

2.

2x + 3y = -17    Multiply by -2

5x + 2y = -4      Multiply by 3

-4x - 6y = 34

15x + 6y = -12

Add last two equations.

11x = 22

x = 2

Substitute x = 2 into first original equation and solve for y.

2x + 3y = -17

2(2) + 3y = -17

4 + 3y = -17

3y = -21

y = -7

Answer: D. (2, -7)

3.

x + y = 50     Keep equation as it is.

0.05x + 0.06y = 2.8     Multiply by -20.

x + y = 50

-x - 1.2y = -56

Add last two equations.

-0.2y = -6

y = 30

Substitute y = 30 in first original equation and solve for x.

x + y = 50

x + 30 = 50

x = 20

Answer: C. (20, 30)

4.

8g - 5h = 7   Keep as is.

4g + 10h = 1    Multiply by -2.

8g - 5h = 7

-8g - 20h = -2

Add last two equations.

-25h = 5

h = -1/5

Substitute h = -1/5 into h of first original equation and solve for g.

8g - 5h = 7

8g - 5(-1/5) = 7

8g + 1 = 7

8g = 6

g = 6/8

g = 3/4

Answer: C. (3/4, -1/5)

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