265.
ա. x + y = 3
x = 1
y = 2
1 + 2 = 3
բ. 2x + y = 1
x = 1
y = 2
1 + 2 ≠ 1
գ. 3x + 2y = 7
x = 1
y = 2
3 + 4 = 7
դ. x² + y² = 3
x = 1
y = 2
1² + 4 ≠ 3:
266.
ա. x + y = 5
x = 3
y = 2
3 + 2 = 5
բ. 3x + y = 5
x = 1
y = 2
3 + 2 = 5
գ. 2x – 3y = 1
x = 5
y = 3
10 – 9 = 1
դ. x² + y² = 9:
268.
ա. x + y + z = 10
x = 3
y = 5
z = 2
3 + 5 + 2 = 10
բ. x² + y² + z² = 25
x = 5
y = -5
z = 5
25 + (-25) + 25
գ. xy + yx + zy = 3
xy = 1
yx = 1
zy = 1
1 + 1 + 1 = 3
դ. xy – yx + yz = 1
xy = 1
yx = 1
yz = 1
1 – 1 + 1 = 1: