Bonjour,
I = (x + 1)(x + 5)
I = x² + 5x + x + 5
I = x² + 6x + 5
J = (4x + 5)(2x + 6)
J = 8x² + 24x + 10x + 30
J = 8x² + 34x + 30
K = (5u + 1)(2 - 3u)
K = 10u - 15u² + 2 - 3u
K = 10u + (-15u²) + 2 + (-3u)
K = 7u - 15u² + 2
L = (-3 + n)(-2n - 5)
L = 6n + 15 - 2n² - 5n
L = n + 15 - 2n²
