The symbol between the x and 2y is missing. If it is a plus sign, then
Anything parallel to x+2y = 4 is going to be of the form x+2y = C where C is some fixed number. The left side stays identical and unchanged. To find the value of C, we plug in (x,y) = (0,0). So replace x with 0 and replace y with 0
x+2y = C
0+2*0 = C
0 + 0 = C
0 = C
C = 0
So the equation of the parallel line is x+2y = 0
Again this is all hinged on the assumption that there is a plus sign between x and 2y
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If the symbol between the x and 2y is a minus sign then
Anything parallel to x-2y = 4 is in the form x-2y = C where C is a constant
Plug in (x,y) = (0,0)
x-2y = C
0 - 2*0 = C
0 - 0 = C
0 = C
C = 0
So the parallel equation is x-2y = 0 only if the symbol between the x and 2y is a minus sign.
