Question

I need help with these

Answer 1

Explanation:

1)

-3x + 5y = -7 (1)

-2x - 4y + 5z = 5 (2)

5x - 2y - 5z = 4 (3)

by adding equation (2) and (3)

-2x - 4y + 5z = 5

5x - 2y - 5z = 4

______________

3x - 6y = 9

3(x - 2y) = 9

x - 2y = 9/3

x - 2y = 3

x = 3 + 2y (4)

substituting value of x from equation (4) into equation (1)

-3(3 + 2y) + 5y = -7

-9 - 6y + 5y = -7

-y = -7 + 9

-y = 2

y = -2

substituting value of y in equation (4)

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

substituting values of x and y in equation (3)

5(-1) - 2(-2) - 5z = 4

-5 + 4 - 5z = 4

-1 - 5z = 4

-5z = 4 + 1

-5z = 5

z = -5/5 = -1

thus,

x = -1

y = -2 and

z = -1