Bonjour,
Résoudre:
1/3x² -x-1=0
x²-3x-3= 0
Δ= (-3)²-4(1)(-3)= 9+12= 21 > 0 alors 2 solutions
x1= (-(-3)-√21)/2(1)= (3-√21)/2= (3-√21)/2
X2= (3+√21)/2
S= { x1 ; x2 }
-x² +(√3x)+3=0
a= -1; b= √3 et c= 3
Δ= (√3)²-4(-1)(3)= 3+12= 15
x1= (-√3-√15)/2(-1)= (√3+√15)/2
x2= (√3-√15)/2
S= { x1; x2 =
8x³+5=(2x+3)³ -(x+1)²
8x³+5=(2x+3)(2x+3)(2x+3) -(x+1)²
8x³+5= (2x+3)(4x²+6x+6x+9)-(x²+2x+1)
8x³+5= (2x+3)(4x²+12x+9)-x²-2x-1
8x³+5= 8x³+24x²+18x+12x²+36x+27-x²-2x-1
8x³+5= 8x³+35x²+52x+26
8x³+5-8x³-35x²-52x-26= 0
-35x²-52x-21= 0
Δ= (-52)²-4(-35)(-21)= -236 < 0 donc pas de solutions, x∉ R