решите систему уравнений:

а) {x^2+y^2=5

{xy=2

в) {2x^2+3x^2+y^2=0

{x^2-xy-y^2=4

б) {x^2-8xy+16y^2=25

{4y^2-xy=5

г) {x^2-3xy+y^2=-1

{8y^2-3xy=2

{x^2+y^2=5,

{xy=2;

x^2+2xy+y^2-2xy=5,

(x+y) ^2-2xy=5;

(x+y) ^2-2*2=5;

(x+y) ^2=9;

[x+y=-3,

[x+y=3;

[y=-3-x,

[y=3-x;

[-x (3+x) = 2,

[x (3-x) = 2;

[x^2+3x+2=0,

[x^2-3x+2=0;

x_1=-2, x_2=-1, x_3=1, x_4=2,

y_1=-1, y_2=-2, y_3=2, y_4=1.

{x^2-8xy+16y^2=25,

{4y^2-xy=5;

{ (x-4y) ^2=25,

{y (4y-x) = 5;

[x-4y=-5,

[x-4y=5;

-y (x-4y) = 5,

[5y=5,

[-5y=5;

y_1=1, y_2=-1;

[x-4=-5,

[x-4 * (-1) = 5;

x_1=-1, x_2=1.