Question

Будь ласкаааа!!!!!! ДОПОМОЖІТЬ ДАЮ 50 БАЛІВ

Answer 1

1)

$\displaystyle\\\left \{ {{x-5y=8} \atop {2x+4y=30}} \right. \\\\\left \{ {{x=8+5y} \atop {2x+4y=30}} \right.\\2(8+5y)+4y=30\\16+10y+4y=30\\14y=14\\y=1= > x=8+5\times1=13$

2)
$\displaystyle\\\left \{ {{2x-y=1} \atop {7x-6y=4}} \right. \\\\\left \{ {{y=2x-1} \atop {7x-6y=4}} \right. \\7x-6(2x-1)=4\\7x-12x+6=4\\-5x=-2\\x=\frac{2}{5} = > y=2\times\frac{2}{5}-1=-\frac{1}{5}$

3)

$\displaystyle\\\left \{ {{5a-3b=14} \atop {2a+b=10}} \right. \\\\\left \{ {{5a-3b=14} \atop {b=10-2a}} \right.\\ 5a-3(10-2a)=14\\5a-30+6a=14\\11a=44\\a=4= > b=10-2\times4=2$

4)

$\displaystyle\\\left \{ {{2x-3y=2} \atop {4x-5y=1}} \right. \\\\\left \{ {{x=\dfrac{2+3y}{2} } \atop {4x-5y=1}} \right. \\\\4\times\frac{2+3y}{2}-5y=1\\ 2(2+3y)-5y=1\\4+6y-5y=1\\y=-3= > x=\frac{2+3\times(-3)}{2}=-\frac{7}{2} =-3\frac{1}{3}$