how do I solve 4x+y=0 and 5x-y=9
\(\left \{ {{4x+Y=0} \atop {5x-Y=9}} \right.\)\((4x+y=0) + (5x-y=9) \\ 9x+y-y=0+9 \\ 9x=9\)\(x=1\)\(4(1)+y=0\)\(y=-4\)
