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Exercice 2 : 

1. J = (x - 7) (3 - 2x) + (5x - 2) (4x - 1)
J = x X 3 + x X (- 2x) - 7 X 3 - 7 X (- 2x) + 5x X 4x + 5x X (- 1) - 2 X 4x - 2 X (- 1)
J = 3x - 2x² - 21 + 14x + 20x² - 5x - 8x + 2
J = 18x² + 4x - 19

K = (x - 7) (3 - 2x) - (5x - 2) (4x - 1)
K = x X 3 + x X (- 2x) - 7 X 3 - 7 X (- 2x) - [5x X 4x + 5x X (- 1) - 2 X 4x - 2 X (- 1)]
K = 3x - 2x² - 21 + 14x - (20x² - 5x - 8x + 2)
K = 3x - 2x² - 21 + 14x - 20x² + 5x + 8x - 2
K = - 22x² + 30x - 23

2. N = (4 + 7x)²
N = 4² + 2 X 4 X 7x + (7x)²
N = 16 + 56x + 49x²

P = (4 - 7x)²
P = 4² - 2 X 4 X 7x + (7x)²
P = 16 - 56x + 49x²

Q = (4 - 7x) (4 + 7x)
Q = 4² - (7x)²
Q = 16 - 49x²