––––––––––––––––––––––––––––––
(x - 2y) + (x + 2y) = 7 + 1
-4y = 8
y = 8 : (-4)
y = -2
––––––––––––––––––––––––––––––
x - 2 * (-3) = 7
x + 4 = 7
x = 7 - 4
x = 3
––––––––––––––––––––––––––––––
ответ: (-2; 3).––––––––––––––––––––––––––––––
2.––––––––––––––––––––––––––––––
(х + 3у) - (х+2у) = 7 - 5
у = 2
––––––––––––––––––––––––––––––
х + 3 * (2) = 7
х + 6 = 7
х = 7 - 6
х = 1
––––––––––––––––––––––––––––––
ответ: (2; 1).––––––––––––––––––––––––––––––
3.––––––––––––––––––––––––––––––
(4х - 6у) + 2 * (5х + 3у) = 26 + 2 * 1
14x = 28
x = 28 : 14
x = 2
––––––––––––––––––––––––––––––
4 * 2 - 6y = 26
8 - 6y = 26
-6y = 26 - 8
-6y = 18
y = 18 : (-6)
y = -3
––––––––––––––––––––––––––––––
ответ: (2; -3).––––––––––––––––––––––––––––––
4.––––––––––––––––––––––––––––––
5 * (3x - 2y) + 2 * (2x + 5y) = 5 * 5 + 2 * 16
19x = 57
x = 57 : 19
x = 3
––––––––––––––––––––––––––––––
3 * 3 - 2y = 5
9 - 2y = 5
7y = 5
y = 7 - 5
y = 2
––––––––––––––––––––––––––––––
ответ: (3; 2).––––––––––––––––––––––––––––––
2)895
3)890
Потому что А=-4;