B1: Tim x
a. ( x - 10 ) : 10 = 20
x - 10 = 20 . 10
x - 10 = 200
x = 200 + 10
x = 210
b. 3 . 3 .3 . x + 5 .5 . x = 104 ( xin loi nha may tinh minh ko danh so mu duoc )
27 . x + 25 . x = 104
x . ( 27 + 25 ) = 104
x . 52 = 104
x = 104 : 52
x = 2
c. x.x.x = x
( x.x.x) - x= 0
x (x.x - 1 ) = 0
suy ra x = 0 hoac x.x - 1 = 0
x.x -1 = 0
x.x = 0+1
x.x = 1
suy ra x .x = 1.1
suy ra x=1