Равносильны ли уравнения: 1) 3x + 2y = 9 и y = 9/2 - 3/2x 2) 7x - 5y = 12 и y = 1/5 (5x - 6) 3) 5x + 3y = 6 и x = 6 - 3y/5 4) |x + y| + |x - y| = -10 и√(2x +y)² + 36 = 0
