Question

Solve, using linear combination. 3x + y = 4. 2x + y = 5. A.. . . (–1, 7). . . B.. . . (–3, 12). . . C.. (0, 4). . . D.. . . (–3, 13).

Answer 1

3x + y = 4....multiply by -1
2x + y = 5
--------------
-3x - y = -4 (result of multiplying by -1)
2x + y = 5
--------------add
-x = 1
x = -1

2x + y = 5
2(-1) + y = 5
-2 + y = 5
y = 5 + 2
y = 7

solution is (-1,7)

Answer 2

3x + y = 4
2x + y = 5
-3x - y = -4 
2x + y = 5
-x = 1
x = -1
2x + y = 5
2(-1) + y = 5
-2 + y = 5
y = 5 + 2
y = 7

solution is (-1,7) hope this helps