To eliminate x, multiply the fist equation by 4:

x - 2y = 4
-4x + 8y = -16 |
4 | 4x - 8y = 16
-4x + 8y = -16 |

Adding gives 0 = 0, which tells us that the second equation is equivalent to the first. Thus, since the system is underdetermined, there are infinitely many solutions. To obtain the general solution, solve the first equation for x, and take y to be arbitrary:

x = 4 + 2y
y is arbitrary |

Enter this as (4 + 2y, y)

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