bonsoir,

a)

1/3 -2 = 7x

1/3-6/3 = 7x

-5/3 = 7x

x = (-5/3 )/ 7

x = -5/3 *1/7

x = -5/21

b)

3+17 = -x² +5x²

20= 4x²

x² = 20/4

x² = 5

x = √5

c)

équation produit nul

soit

-9x+3 =0

-9x =-3

x = 3/9

x= 1/3

soit

-x+7 = 0

x = -7