А)
{ху+5х+3у+15=ху+8х+у+8
{10ху+14х-15у-21=10ху+10х-12у-12
{ху+5х+3у-ху-8х-у=8-15
{10ху+14х-15у-10ху-10х+12у=21-12
{2у-3х=-7 ||×4
{4х-3у=9 ||×3
{8у-12х=-28
{12х-9у=27
8у-12х+12х-9у=27-28
-у=-1
у=1
4х-3×1=9
4х-3=9
4х=12
х=3
(3;1)
=================
б)
{ху-2х+5у-10=ху-х+2у-2
{ху+7х-4у-28=ху+4х-3у-12
{ху-2х+5у-ху+х-2у=-2+10
{ху+7х-4у-ху-4х+3у=-12+28
{-х+3у=8 ||×3
{3х-у=16
{-3х+9у=8
{3х-у=16
-3х+9у+3х-у=8+16
8у=24
у=3
х=3у-8=3×3-8=1
(1;3)
================
в)
{6х-ху+24-4у=9х-ху+18-2у
{24х-10ху-12+5у=20х-10ху-4+2у
{6х-ху-4у-9х+ху+2у=18-24
{24х-10ху+5у-20х+10ху-2у=-4+12
{-3х-2у=-6 ||×3
{4х+3у=8 ||×2
{-9х-6у=-18
{8х+6у=16
-9х-6у+8х+6у=-18+16
-х=-2
х=2
4×2+3у=8
8+3у=8
3у=0у=0
(2;0)