Question

3 і 5 дуже потрібно будь ласка

Answer 1

$\displaystyle\bf\\3)\\\\\left \{ {{2x+5y=15} \ |\cdot(-3)\atop {3x+8y=-1} \ |\cdot 2} \right. \\\\\\+\left \{ {{-6x-15y=-45} \atop {6x+16y=-2}} \right.\\ -----------\\y=-47\\\\2x=15-5y=15-5\cdot(-47)=15+235=250\\\\x=250:2=125\\\\Otvet \ : \ (125 \ ; \ -47)$

$\displaystyle\bf\\\left5 )\ \{ {{6x-y+1=0} \atop {4x-5y+17=0}} \right. \\\\\\\left \{ {{6x-y=-1} \atop {4x-5y=-17} } \right.\\\\\\\left \{ {{y=6x+1} \atop {4x-5\cdot(6x+1)=-17}} \right.\\\\\\\left \{ {{y=6x+1} \atop {4x-30x-5=-17}} \right. \\\\\\\left \{ {{y=6x+1} \atop {-26x=-17+5}} \right. \\\\\\\left \{ {{x=\dfrac{6}{13} } \atop {y=6\cdot\dfrac{6}{13}+1 }} \right. \\\\\\\left \{ {{x=\dfrac{6}{13} } \atop {y=2\dfrac{10}{13} +1 }} \right.$

$\displaystyle\bf\\\left \{ {{x=\dfrac{6}{13} } \atop {y=3\dfrac{10}{13} }} \right.\\\\\\Otvet \ : \ \Big(\frac{6}{13} \ ; \ 3\frac{10}{13} \Big)$