bjr

ex 3

-2x (7 - 4x) = -2x*7 - 2x*(-4x) = -14x + 8x²

puisque k(a+b) =ka + kb

(4-1/3x)  (-3x - 5/2) =

4 * (-3x) + 4 * (-5/2) + (-1/3x) * (-3x) + (-1/3x) * (-5/2)

puisque (a+b) (c+d) = ac + ad + bc + bd

je te laisse calculer et réduire

(1 - √2x) (1 + √2x) = 1² - (√2x)²

tu finis

(2/3 + 3x)² = (2/3)² + 2*2/3*3x + (3x)²  tu finis

(1/2x - 4)² = (1/2x)² - 2*1/2x4 + 4²   tu finis

factorisation

(x-3)² + (x-3) (2x-8) = (x-3) ((x-3 + 2x-8) = (x-3) (3x-11)

x² + 6x + 8 =

25 - 4x² = 5² - 4x² = (5+4x) (5-4x)

x² + 12x + 36 = (x + 6)²

4x² - 36x + 81 = (2x - 9)²