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y = 2x - 8     rearrange as     2x - y  = 8

2x - y  = 8

Note that these equations are exactly the same.....anytime we have that, NSS, we will have infinite solutions....!!!  [dependent ]

-2x  - y  = 1      multiply through by 2  →   -4x - 2y  =  2

-4x - 2y  = -1

Note, NSS.......when one equation equals one thing and the same equation equals something else, we will have no solutions.......

Think about this......if I add or subtract two quantities....I get some result

So.....if I add or subtract the same two quantites....it will be impossible to get something different from the first result.....!!!!