<span>1) 3,(2х-1)-(-7х+4)+5(-х-3) при х=-2</span>
3(2*(-2)-1)-(7*(-2)+4)+5(2-3)
3*(-3)-18+10-15
-9-18-5=-32
<span>1) 3,(2х-1)-(-7х+4)+5(-х-3) при х=-2</span>
6х-3+7х+4+5х-15=0
6х+7х+5х=3-4+15
18х=14
х=14/18=7/9
<span>2)-4(-0,8х+2у)-(4,2х-у) при х=2, у=-1</span>
<span>-4(-0,8*2+2*(-1)-(4,2*2-1)</span>
<span>-4(-1,6-2)-7,4</span>
<span>-4*(-8,1)-7,4=25</span>
<span>2)-4(-0,8х+2у)-(4,2х-у) при х=2, у=-1</span>
<span>3,2х-8у-4,2х-у=0</span>
<span>3,2х-4,2х=8у+у</span>
<span>-1х=9у |:(-1)</span>
<span>х=-9у</span>