а) {3x+2y=5 {y=(5-3x)/2 {y=(5-3x)/2 {y=(5-3x)/2
{2x^2+3y=12 {2x^2+3((5-3x)/2) {2x^2+(15-9x)/2=12 {(4x^2+15-9x)/2=12
{y=(5-3x)/2 {4x^2+15-9x
{4x^2+15-9x=24
4x^2+15-9x-24=0; D=81+144=225=15^2; x=(9+15)/8=3. x=(9-15)/8=-0.75
{x=3 {x=-0.75
{y=(5-3*3)/2=-2 {y=(5-3(-0.75))/2=11/8
б) {x+y=3 {x=3-y {x=3-y {x=3-y {y=-9
{x^2+2xy+2y^2=18 {(3-y)^2+2(3-y)*y+2y^2=18 {9-y=18 {y=-9 {x=12
в) {x-4y=-1 {x=-1+4y {x=-1+4y {x=-1+4y {y=1
{3x-y=8 {3(-1+4y)-y=8 {-3+11y=8 {y=1 {x=3
г) {x+y=10 {x=10-y {x=10-y {x=10-y {y=3
{x^2-y^2=40 {(10-y)^2-y^2=40 {-20y=-60 {y=3 {x=7