aidez moi plzzz x²-x-1= (x-1/2)²-5/4

x²-x-1= (x-1/2)²-1/4-1= (x-1/2)²-1/4-4/4=(x-1/2)²-5/4
donc VRAIE, tu as parfaitement bon car tu as utilisé la forme canonique!!!

x² -x -1 = (x -1/2)² -5/4
x² -x -1 = x² -1/2x -1/2x + 1/4 -5/4
x² -x² -x = -2/2x +1/4 -5/4
-x = x  +1/4 -5/4
-x -x = 1/4 -5/4
-2x = -4/4
-2x = -1
x = -1/ -2
x= 0,5