Question

Tìm số tự nhiên x, biết:

a. 219 - 7(x+1) = 100

b. (3x - 6) . 3 = 3⁴

Answer 1

a. 219 - 7(x+1) = 100

    7(x+1)=119

     x+1=119:7

    x+1=17

    x=16

Vậy x=16

b. (3x - 6) . 3 = 3⁴

     3x-6=3⁴:3

     3x-6=3³

     3x=33

    x=11

Vậy x=11  

Answer 2

a) \(219-7\left(x+1\right)=100\)

\(\Leftrightarrow219-7x-7=100\)

\(\Leftrightarrow-7x=100-219+7=-112\)

\(\Leftrightarrow x=16\)

b) \(\left(3x-6\right)\cdot3=3^4\)

\(\Leftrightarrow\left(x-2\right)\cdot3^2=3^4\)

\(\Leftrightarrow x-2=3^2\)

\(\Leftrightarrow x=9+2=11\)

Answer 3

a) \(219-7\left(x+1\right)=100\)

\(\Rightarrow7\left(x+1\right)=119\)

\(\Rightarrow x+1=119:7\)

\(\Rightarrow x+1=17\)

\(\Rightarrow x=16\)

b) \(\left(3x-6\right)3=3^4\)

\(\Rightarrow\left(3x-6\right)=3^3:3\)

\(\Rightarrow\left(3x-6\right)=3^3\)

\(\Rightarrow\left(3x-6\right)=27\)

\(\Rightarrow3x=27-6\)

\(\Rightarrow3x=21\)

\(x=21:3\)

\(\Rightarrow x=7\)