y⁴ + 2y² - 5y + 1 = (y⁴ + 2y² + 1) - 5y = (y² + 1)² - 5y
y⁴ + 2y² - 5y + 1 = (1/2)⁴ + 2·(1/2)² - 5·(1/2) + 1 = 1/16 + 1/2 - 2,5 + 1 = -0,9375
y⁴ + 2y² - 5y + 1 = (y⁴ + 2y² + 1) - 5y = (y² + 1)² - 5y
y⁴ + 2y² - 5y + 1 = (1/2)⁴ + 2·(1/2)² - 5·(1/2) + 1 = 1/16 + 1/2 - 2,5 + 1 = -0,9375