\(7^{2x-6}=49\\ \Rightarrow7^{2x-6}=7^2\\ \Rightarrow2x-6=2\\ \Rightarrow2x=8\\ \Rightarrow x=4\)

7^2x-6=7²

2x-6=2

2x=2+6

2x=8

x=4

\(7^{2x-6}=49\)

\(=>7^{2x-6}=7^2\) hoặc \(7^{2x-6}=\left(-7\right)^2\)

\(=>2x-6=7\) hoặc \(2x-6=-7\)

\(=>2x=7+6\) hoặc \(2x=\left(-7\right)+6\)

\(=>2x=13\) hoặc \(2x=-1\)

\(=>x=\dfrac{13}{2}\) hoặc \(x=-\dfrac{1}{2}\)

Vậy \(x=\dfrac{13}{2}\) hoặc \(x=\dfrac{-1}{2}\)

\(#NqHahh\)

\(7^{2x-6}=49\)

\(\Rightarrow7^{2x-6}=7^2\)

\(\Rightarrow2x-6=2\)

\(\Rightarrow2x=2+6\)

\(\Rightarrow2x=8\)

\(\Rightarrow x=8:2=4\)

Lời giải:
$7^{2x-6}=49=7^2$

$\Rightarrow 2x-6=2$

$\Rightarrow 2x=8$

$\Rightarrow x=4$

a) (x - 1)² = 1.

<=> x - 1 = 1 hoặc x - 1 = -1.

<=> x = 2 hoặc x = 0.      

b) 7^{2x - 6} = 49.

<=> 7^{2x - 6} = 7².   

<=> 2x - 6 = 2.

<=> x = 4.  

c) (2x - 16)⁷ = 128.

<=> (2x - 16)⁷ = 2⁷.

<=> 2x - 16 = 2.

<=> x = 9.

cho hỏi sao phân tích ra x-1=-1 vậy

\(a,x.\left(x+3\right)=0\)

\(\Rightarrow\orbr{\begin{cases}x=0\\x+3=0\end{cases}\Rightarrow\orbr{\begin{cases}x=0\\x=-3\end{cases}}}\)

\(b,30.\left(x+2\right)-6\left(x-5\right)-24x=100\)

\(30x+60-6x-30-24x=100\)

\(x.\left(30+60-6-30-24\right)=100\)

\(x.30=100\)

\(x=\frac{10}{3}\)

72x(28-49)+28x(-49-72)

=72x(-21)+28x(-121)

=-1512+(-3388)

=-49900

Có 2 cách hiểu 

+ ) 72x( 28 - 49 ) + 28x( -49 - 72)

= 72x . 28 - 72x . 49 - 28x . 49 - 28x . 72 

= -72x . 49 - 28x . 49

= 49 . ( - 100x )

+) 72 . ( 28 - 49 ) + 28 . ( -49 - 72 )

= 72 . 28 - 72 . 49 -28 . 49 - 28 . 72

= -72 . 49 -28 . 49

= 49 . ( -100 ) = -4900

cái này là tìm x phải ko bn

a)27³-72x=0

-72x=27³

^=>x=27³/-72

x=-273,375

b)=>(x+2)²=6.(x+2)

(x+2)²/(x+2)=6

(x+2)=6

vậy x =6-2=4