bjr

x² - 25 = (x)² - (5)² = (x+5) (x-5) puisque a² - b² = (a+b) (a-b)

(x+2) (3x-1) = x*3x + x*(-1) + 2*3x + 2*(-1) = 3x² -x + 6x - 2 = 3x² + 5x - 2

4x² + 3x = 4*x* + 3*x = x(4x+3)

28 = 2x14 = 2x2x7 = 2²x7

diagonale rectangle de 10 cm x 20 cm

diag² = 10² + 20² = 500          (pythagore)

=> diag ≈ 22 cm