Question

54:19 To eliminate the terms and solve for y in the fewest steps, by which constants should the equations be multiplied by before adding the equations together? First equation: 9x + 3y = -18 Second equation: 8x + 7y = 10 The first equation should be multiplied by 3 and the second equation by 7. The first equation should be multiplied by -3 and the second equation by -7. The first equation should be multiplied by - 7 and the second equation by 3 . The first equation should be multiplied by -7 and the second equation by -3.

Answer 1

The first equation should be multiplied by - 7 and the second equation by 3

Explanation:

Given

`9x + 3y = -18` -- (1)

`8x + 7y = 10` -- (2)

Required

How to eliminate y

In (1), the coefficient of y = 3

In (2), the coefficient of y = 7

Multiply the first equation by -7

`-7(9x + 3y = -18)`

`-63x -21y = 126` --- (3)

Multiply the second by 3

`3(8x + 7y = 10)`

`24x + 21y = 30` -- (4)

Add the results together:

`-63x -21y = 126`

`24x + 21y = 30`

`-------------------------`

`-63x + 24x -21y +21y = 126+30`

`-63x + 24x = 126+30`

See that y is eliminated