{x^2+10xy+25y^2=9
{x-5y=7
{(х+5у)^2=9
{x-5y=7
{(х+5у)^2=9
{x= 7+5у
{(7+ 5у + 5у)^2=9
{x= 7+5у
{(7+ 5у + 5у)^2=9
{5у= х-7
{(7+ 5у + 5у)^2=9
{у= (х-7)/5
(7+ 5у + 5у)^2=9
(7+ 10у)^2=9
49 + 140у + 100у^2= 9
49 + 140у + 100у^2 - 9=0
100у^2 + 140у + 40= 0
Д= 140^2 - 4×100×40= 19600 - 16000= 3600
корень из Д= 60
х1= (-140+60)/2×100= -80/200= -0.4
х2= (-140-60)/2×100= -200/200= -1
{х1= -0.4
{у1= (-0.4 - 7)/5
{х2= -1
{у2= (-1 - 7)/5
{х1= -0.4
{у1= -7.4/5
{х2= -1
{у2= -8/5
{х1= -0.4
{у1= -1.48
{х2= -1
{у2= -1.6
ответ: (-0.4; -1.48); (-1; -1.6).
