Question

Решите пожалуйста дам 30 балов 470 номер только а б

Answer 1

$\displaystyle\bf\\1)\\\\\left \{ {{7x+4y=23} |\cdot(-8)\atop {8x-10y=19}|\cdot 7} \right. \\\\\\+\left \{ {{-56x-32y=-184} \atop {56x-70y=133}} \right. \\------------\\-102y=-51\\\\y=0,5\\\\7x=23-4y=23-4\cdot 0,5=23-2=21\\\\x=21:7=3\\\\Otvet \ : \ (3 \ ; \ 0,5)\\\\2)\\\\\left \{ {{5x-4y=16} \atop {2x-4y=12} \ |\cdot (-1)} \right. \\\\\\+\left \{ {{5x-4y=16} \atop {-2x+4y=-12}} \right.\\ -----------\\3x=4\\\\x=1\frac{1}{3}$

$\displaystyle\bf\\4y=2x-12=2\cdot1\frac{1}{3} -12=2\frac{2}{3} -12=-9\frac{1}{3} \\\\\\y=-9\frac{1}{3} :4=-\frac{28}{3} \cdot \frac{1}{4} =-\frac{7}{3} =-2\frac{1}{3} \\\\\\Otvet \ : \ \Big(1\frac{1}{3} \ ; \ -2\frac{1}{3} \Big)$