Bonsoir,
a) 2x + 1 = 13
2x = 13 - 1
2x = 12
x = 12/2
x = 6
b) 14 = 20 - 3x
3x = 20 - 14
3x = 6
x = 6/3
x = 2
c) pas sur de l'écriture de l'équation : c'est 1/7 ou (2x + 1)/7
d) 3x - 5 = 2x + 10
3x - 2x = 10 + 5
x = 15
e) 10x + 3 = 7x - 1
10x - 7x = -3 - 1
3x = -4
x = -4/3
À toi de faire le reste, je te donne le résultat
f) 3x = 8x + 16
x = -16/5
a) 2x + 4 = -x + 28
x = 8
b) 10x + 3 = 5x + 45
x = 42/5
c) x^2 + 2x + 20 = 100
x^2 + 2x + 20 - 100 = 0
x^2 + 2x - 80 = 0
Delta = 2^2 - 4 * 1 * (-80)
Delta = 4 + 320
Delta = 324
Vdelta = V324 = 18 > 0 donc deux solutions
X1 = (-2-18)/2
X1 = -20/2
X1 = -10
X2 = (-2+18)/2
X2 = 16/2
X2 = 8
d) -2x^2 + 8 = -15x
2x^2 - 15x - 8 = 0
Delta = (-15)^2 - 4 * 2 * (-8)
Delta = 225 + 64
Delta = 289
Vdelta = V289 = 17 > 0 donc deux solutions
X1 = (15-17)/4
X1 = (-2)/4
X1 = (-1/2)
X2 = (15+17)/4
X2 = 32/4
X2 = 8
