Question

tìm x e N biết

a)541+(218-x)=735

b)96-3.(x+1)=42

c)(x-36):18=12

d)3^x + 3^x+1 +3^x+2 =13.81

Answer 1

a, 541 + ( 218 - x ) = 735

=> 218 - x = 735 - 541

=> 218 - x = 194

=> x = 218 - 194

=> x = 24

Vậy x = 24

b, 96 - 3.( x + 1 ) = 42

=> 3.( x + 1 ) = 96 - 42

=> 3.( x + 1 ) = 54

=> x + 1 = 54 : 3

=> x + 1 = 18

=> x = 18 - 1

=> x = 17

Vậy x = 17

c, ( x - 36 ) : 18 = 12

=> x - 36 = 12.18

=> x - 36 = 216

=> x = 216 + 36

=> x = 252

Vậy x = 252

d, 3^x + 3^x+1 + 3^x+2 = 13.81

=> 3^x.1 + 3^x.3 + 3^x.3²= 13.81

=> 3^x.( 1 + 3 + 3² ) = 13.81

=> 3^x.( 1 + 3 + 9 ) = 13.81

=> 3^x.13 = 13.81

=> 3^x= 13.81:13

=> 3^x= 81

=> 3^x = 3⁴

=> x = 4

Vậy x = 4