[latex]16.\egin{cases} 2x+4=4y\y-4x=1 end{cases}\ \egin{cases} 2x-4y=-4/*2\-4x+y=1 end{cases}\ \egin{cases} 4x-8y=-8\-4x+y=1 end{cases}\----------\-7y=-7/:(-7)[/latex] [latex]y=1\ \2x+4=4*1\ \2x=4-4\ \x=0\ \egin{cases} x=0\y=1 end{cases}[/latex] [latex]17.\egin{cases} 6+y=3x\ x-3=2y end{cases}\ \egin{cases} -3x+y=-6\ x-2y=3/*3end{cases}\ \egin{cases} -3x+y=-6\ 3x-6y=9end{cases}\----------\-5y=3/:(-5)[/latex] [latex]y=-frac{3}{5}\ \6-frac{3}{5}=3x\ \3x=5frac{2}{5}/*(-frac{1}{3})\ \x=frac{27}{5}*frac{1}{3}[/latex] [latex]x=frac{9}{5}\ \x=1frac{4}{5}\ \egin{cases} x=1frac{4}{5}\ \y=-frac{3}{5} end{cases}[/latex] [latex]19.\egin{cases} 2x+16y=10\3x-y=15/*16 end{cases}\ \egin{cases} 2x+16y=10\48x-16y=240end{cases}\----------\50x=250/:50\ \x=5[/latex] [latex]3*5-y=15\ \15-y=15\ \y=15-15\ \y=0\ \egin{cases} x=5\y=0 end{cases}[/latex] [latex]20.\egin{cases} 4x+y=-5/*3\ 2x-3y=16end{cases}\ \egin{cases}12x+3y=-15\ 2x-3y=16end{cases}\----------\14x=1/:14\ \x=frac{1}{14}[/latex] [latex]4*frac{1}{14}+y=-5\ \frac{2}{7}+y=-5\ \y=-5-frac{2}{7}[/latex] [latex]y=-5frac{2}{7}\ \egin{cases} x=frac{1}{14}\ \y=-5frac{2}{7} end{cases}[/latex] [latex]21.\egin{cases} x+2y=8\ 4x-y=15/*2end{cases}\ \egin{cases}x+2y=8\ 8x-2y=30end{cases}\----------\9x=38/:9\ \x=frac{38}{9}[/latex] [latex]x=4frac{2}{9}\ \4frac{2}{9}+2y=8\ \2y=8-4frac{2}{9}\ \2y=3frac{7}{9}/*frac{1}{2}\ \y=frac{34}{9}*frac{1}{2}[/latex] [latex]y=frac{17}{9}\ \y=1frac{8}{9}\ \egin{cases} x=4frac{2}{9}\ \y=1frac{8}{9} end{cases}[/latex] [latex]22.\egin{cases}2x+y=-5/*3\ x-3y=20end{cases}\ \egin{cases}6x+3y=-15\ x-3y=20end{cases}\----------\7x=5/:7\ \x=frac{5}{7}[/latex] [latex]2*frac{5}{7}+y=-5\ \frac{10}{7}+y=-5\ \y=-5-frac{10}{7}\ \y=-5-1frac{3}{7}[/latex] [latex]y=-6frac{3}{7}\ \egin{cases} x=frac{5}{7}\ \y=-6frac{3}{7} end{cases}[/latex]
