Question

Tìm x 

13 - 2 ( x + 1 ) = 7

6x + 2³ = 5² . 2 

420 + 56 . 4 = ( x + 175 ) : 5 + 30 

x + 2 . x + 3x + .... + 9x = 450 

Answer 1

13 - 2(x + 1) = 7

=> 2(x + 1) = 13 - 7 = 6

=> (x + 1) = 6 : 2 = 3 

=> x = 2

6x + 2³ = 5². 2

=> 6x + 8 = 25. 2

=> 6x + 8 = 50

=> 6x = 50 - 8 = 42

=> x = 7

x + 2 . x + 3x + .... + 9x = 450 

x.(1+ 2 + 3 + ... + 9) = 450

x. 45 = 450 

=> x = 450 : 45 = 10

Answer 2

1) 13-2(x+1)=7

<=>2(x+1)=6

<=>x+1=3

<=>x=2

2) 6x+2³=5².2

<=>6x=42

<=>x=7

3) 420+56.4=(x+175):5+30

<=>644-30=(x+175):5

<=>614x5=x+175

<=>3070-175=x

<=>x=2895

4) x+2x+3x+...+9x=450

<=>x(1+2+3+...+9)=450

<=>45x=450

<=>x=10