What equation is equivalent to [tex][tex]$9^{x-3}=729$[/tex][/tex]?

A. [tex][tex]$9^{x-3}=9^{81}$[/tex][/tex]

B. [tex][tex]$9^{x-3}=9^3$[/tex][/tex]

C. [tex][tex]$3^{x-3}=3^6$[/tex][/tex]

D. [tex][tex]$3^{2(x-3)}=3^6$[/tex][/tex]



Answer :

To determine which equation is equivalent to [tex]\( 9^{x-3} = 729 \)[/tex], let's rewrite the equation in different forms and analyze the options given.

First, we need to express [tex]\( 729 \)[/tex] as a power of [tex]\( 9 \)[/tex]:
[tex]\[ 9^{x-3} = 729 \][/tex]

To find this power, note that [tex]\( 9 \)[/tex] can be written as [tex]\( 3^2 \)[/tex]:
[tex]\[ 9 = 3^2 \][/tex]

Then [tex]\( 9 \)[/tex] raised to any power [tex]\( y \)[/tex] can be written as:
[tex]\[ 9^y = (3^2)^y = 3^{2y} \][/tex]

Thus, [tex]\( 9^{x-3} \)[/tex] can be rewritten as:
[tex]\[ 9^{x-3} = (3^2)^{x-3} = 3^{2(x-3)} \][/tex]

We need to express [tex]\( 729 \)[/tex] as a power of [tex]\( 3 \)[/tex]:
[tex]\[ 729 = 3^6 \][/tex]

So the equation becomes:
[tex]\[ 3^{2(x-3)} = 3^6 \][/tex]

Since the bases are the same, we can equate the exponents:
[tex]\[ 2(x-3) = 6 \][/tex]

Simplify the equation:
[tex]\[ 2x - 6 = 6 \][/tex]
[tex]\[ 2x = 12 \][/tex]
[tex]\[ x = 6 \][/tex]

Now, let’s go back to the options to find the one that matches this transformed equation:
1. [tex]\( 9^{x-3} = 9^{81} \)[/tex]
2. [tex]\( 9^{x-3} = 9^3 \)[/tex]
3. [tex]\( 3^{x-3} = 3^6 \)[/tex]
4. [tex]\( 3^{2(x-3)} = 3^6 \)[/tex]

Option (2) reads [tex]\( 9^{x-3} = 9^3 \)[/tex].

By comparing it with [tex]\( 9^{x-3} = 729 \)[/tex], and since we found [tex]\( 729 = 9^3 \)[/tex], this option is correct.

Therefore, the equation equivalent to [tex]\( 9^{x-3} = 729 \)[/tex] is:
[tex]\[ 9^{x-3} = 9^3 \][/tex]