x + x * 2,7 + x * 6,3 = 120

x * 1 + x * 27 + x * 63 = 120

x * ( 1 + 2,7 + 6,3 ) = 120

x * 10 = 120

x = 120 : 10

x = 12 

x+x*2,7+x*6,3=120

x(1+ 2,7 + 6,3) = 120

x* 10 = 120

x= 12 

219 - 7(x + 1) = 10²

7(x + 1) = 219 - 10²

7(x + 1) = 219 - 100

7(x + 1) = 119

x + 1 = 119 : 7

x + 1 = 17

x = 17 - 1

x = 16

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(3x - 2⁴) . 7³ = 2.7⁴

(3x - 16).7³ = 2.7⁴

3x - 16 = 2.7⁴:7³

3x - 16 = 2.7

3x - 16 = 14

3x = 14 + 16

3x = 30

x = 30 : 3

x = 10

Lời giải:

$10+2x=4^5:4^3=4^2=16$

$2x=16-10=6$

$x=6:2=3$

---------

$2x-6^2:18=3.2^2$
$2x-2=12$

$2x=14$

$x=14:2=7$

--------------

$70-5(x-3)=3.2^5=96$

$5(x-3)=70-3.2^5=-26$

$x-3=\frac{-26}{5}$

$x=3+\frac{-26}{5}=\frac{-11}{5}$

------------------

$19-7(x+1)=10^2=100$

$7(x+1)=19-100=-81$

$x+1=\frac{-81}{7}$

$x=\frac{-81}{7}-1=\frac{-88}{7}$

------------

$(3x-2^4).7^3=2.7^4$

$3x-16=2.7^4:7^3=2.7=14$

$3x=14+16=30$

$x=30:3=10$

(3.x - 2^4) . 7^3 = 2. 7^4

(3.x - 16) . 343 = 2 . 2401

(3.x - 16) . 343 = 4802

3.x - 16 = 4802 : 343 

3.x - 16 = 14

3.x = 14 + 16

3.x = 30

x = 30 : 3

x = 10

7^x+2+2.7^x-1=345

=>7^x-1(7³+2)=345

=>7^x-1=345:345=1

=>x-1=0

=>x=1

7^x-1 . 7^x+3 + 2. 7^x-1 = 345

7^x-1 .(7^x+3 + 2)  =345

7^x-1. (7^x+3 + 2) = 7^x+3 -2

7^x-1                    =(7^x+3 - 2) : (7^x+3 +2)

7^x-1                    = 0

=> x-1                  = 1

chắc chắn luôn

2,5 x 2,7 < X x 2 < 2,7 x 4,5 

6,75 < X x 2 < 12,15 

=> x = 4 ; 5 , 6 

<=>6.75<Xx2<12.15

=>X=4;5;6

2,3 x 2,7 < X x 2 < 2,7 x 4,5

6,75 < X x 2 < 12,15

=> x = 4 ; 5 ; 6