hello :
2x+7y=1 ...(*)
y=4x−8...(**)
(4;8) means x= 4 and y= 8
put this values in (*) and(**) :
2(4)+7(8) =1 62=1 false
8=4(4)-8 8=8 true
so :(4;8) is not solution for this system.
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