а) P(x) = (2x + 3) + (5x - 7) - (-1 + 7x) = 2x + 3 + 5x - 7 + 1 - 7x = 0
б) a(x) = (2x + 3)(5x - 7) + (-1 + 7x)(-2x) = 10x^2 - 14x + 15x - 21 + 2x^2 = 12x^2 + x - 21
в) z(x) = (2x + 3)^2 - (5x - 7)^2 + (-1 + 7x)^2 = (4x^2 + 12x + 9) - (25x^2 - 70x + 49) + (1 - 14x + 49x^2) = 4x^2 + 12x + 9 - 25x^2 + 70x - 49 + 1 - 14x + 49x^2 = 28x^2 + 68x - 39
а) P(x) = (2x + 3) + (5x - 7) - (-1 + 7x) = 2x + 3 + 5x - 7 + 1 - 7x = 0
б) a(x) = (2x + 3)(5x - 7) + (-1 + 7x)(-2x) = 10x^2 - 14x + 15x - 21 + 2x^2 = 12x^2 + x - 21
в) z(x) = (2x + 3)^2 - (5x - 7)^2 + (-1 + 7x)^2 = (4x^2 + 12x + 9) - (25x^2 - 70x + 49) + (1 - 14x + 49x^2) = 4x^2 + 12x + 9 - 25x^2 + 70x - 49 + 1 - 14x + 49x^2 = 28x^2 + 68x - 39