Réponse :
Explications étape par étape
J = (x + 7) (3 - 2x) + (5r - 2) (4x + 1)
⇔ J = 3x - 2x² + 21 - 14x + 20xr + 5r - 8x - 2
⇔ J = -2x² - 19x + 20xr + 5r + 19
K= (5x - 2) (5.r - 8) - (3x - 5) (x + 7)
⇔ K = 25xr - 40x - 10r + 16 - ( 3x² + 21x - 5x - 35 )
⇔ K = 25xr - 40x - 10r + 16 - 3x² - 21x + 5x + 35
⇔ K = -3x² - 56x + 25xr - 10r + 51
L = (2x + 3) (5.x - 8) - (2r - 4) (5.r - 1)
⇔ L = 10x² - 16x + 15x - 24 - ( 10r² - 2r - 20r + 4 )
⇔ L = 10x² - 16x + 15x - 24 - 10r² + 2r + 20r - 4
⇔ L = 10x² - 10r² - x + 22r - 28
