Question

Tìm x thuộc N biết :

a. 288 - ( 3x - 359 ) = 140

b. ( 3x - 2)² = 49

c. 1 + 2 + 3 + ..... + x = 136

Làm đầy đủ chính xác nhất mik tick ...

Answer 1

a) \(288-\left(3x-359\right)=140\)

\(3x-359=288-140\)

\(3x-359=148\)

\(3x=507\)

\(x=169\)

vay \(x=169\)

b) \(\left(3x-2\right)^2=49\)

\(\left(3x-2\right)^2=7^2\)

\(\Rightarrow3x-2=7\)

\(\Rightarrow3x=9\)

\(\Rightarrow x=3\)

vay \(x=3\)

Answer 2

288-(3x-359)=140

3x-359=288-140

3x=148+359

x=507:3

x=169

Vay x=169

Answer 3

a)  288 - ( 3x - 359 ) = 140

     3x - 359 = 288 - 140

     3x - 359 = 148

     3x =148 + 359 

     3x = 507

     x = 507 : 3

     x = 169

b) \(\left(3x-2\right)^2=49\)

    \(\left(3x-2\right)^2=7^2\)

     3x - 2 = 7

     3x = 7 + 2

     3x = 9

     x = 9 : 3

     x = 3

c) 1 + 2 + 3 + ..... + x = 136

=> ( 1 + x ) . x : 2 = 136

      ( 1 + x ) . x = 136 . 2

      ( 1 + x ) . x = 272

      ( 1 + x ) . x = 17 . 16

 => x = 16