To eliminate the y-terms and solve for x in the fewest steps, by which constants should the equations be multiplied?

First Equation: 5x - 4y = 28

Second equation: 3x - 9y = 30

The first equation should be multiplied by 3 and the second equation by 5.

The first equation should be multiplied by 3 and the second equation by - 5.

The first equation should be multiplied by 9 and the second equation by 4.

The first equation should be multiplied by 9 and the second equation by - 4.

Question

Mathematics

Mylee

12 June, 18:33

To eliminate the y-terms and solve for x in the fewest steps, by which constants should the equations be multiplied?

First Equation: 5x - 4y = 28

Second equation: 3x - 9y = 30

The first equation should be multiplied by 3 and the second equation by 5.

The first equation should be multiplied by 3 and the second equation by - 5.

The first equation should be multiplied by 9 and the second equation by 4.

The first equation should be multiplied by 9 and the second equation by - 4.

+4

Answers (1)

Know the Answer?

Rhys Logan · Answer 1

The first equation should be multiplied by 9 and the second equation by 4

9 (5x - 4y) = 9 (28)

4 (3x - 9y) = 4 (30)

45x - 36y = 252 ⇒ 45x - 36y = 252

- (12x - 36y = 120) ⇒ - 12x + 36y = - 120

33x + 0 = 132

33x = 132

x = 132/33

x = 4

5x - 4y = 28

5 (4) - 4y = 28

20 - 4y = 28

-4y = 28 - 20

-4y = 8

y = 8/-4

y = - 2

x = 4; y = - 2

3x - 9y = 30

3 (4) - 9 (-2) = 30

12 + 18 = 30

30 = 30