bonsoir
1) 4x-5=9x+4
4x-9x=4+5
-5x=9
x= -9/5 juste
2) 5x/4=21/9
5x*9=4*21
45x=84
x=84/45 juste
3) 3-x=10x-7
-x-10x=-7-3
-11x=-10
x=10/11 juste
4) 1/5+3/4x=8/9-6/7x
21/28x+24/28x=40/45-9/45
45/28x =31/45
x= 31/28
5) (x-7)²=(x+4)²
(x-7)²-(x+4)² =0
(x+7+x+4)(x-7-x-4) =0
(2x+11)(-11) =00
2x+11 =0
2x =-11
x = -11/2
6) √5x(√6x-4)=-2x
V30-4V5+2x =0
-2x = -V30+4V5
x =(-V30+4V5)/-2