Question

12.19(б) {6х+3 = 8х-3(2у-4) 2(2х-3у )-4х =2у-8 12.21 (в) { 3х+2у х-3у + =3 5 6

Answer 1

$\left \{ {{6x+3=8x-6y+12} \atop {4x-6y-4x=2y-8}} \right. = \left \{ {{-2x+6y=9} \atop {-8y=-8 \ = y=1}} \right. -2x+6*1=9 \\ -2x=9-6 \\ -2x=3 \\ x=-1,5 \\ (-1,5;1)$

$\left \{ {{ \frac{3x+2y}{5} + \frac{x-3y}{6} =3|*30} \atop {2x+7y+43=0}} \right. = \left \{ {{ 6(3x+2y)+5(x-3y)=90} \atop {2x+7y+43=0}} \right. = \\ \left \{ {{ 18x+12y+5x-15y=90} \atop {2x+7y+43=0}} \right. =\left \{ {{ 23x-3y=90|*7} \atop {2x+7y=-43|*3}} \right. = \\ +\left \{ {{ 161x-21y=630} \atop {6x+21y=-129}} \right. 167x=501=x=3 \\ 2*3+7y=-43 \\ 7y=-43-6 \\ 7y=-49 \\ y=-7 \\ (3;-7)$