What is the inverse of the function f(x) = 2x-10?

The answer is:  " f ⁻¹(x)  =  x + 5 " .
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Explanation:
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Given the function:  " f(x) = 2x − 10 " ;  Find the inverse of this function ;
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Explanation:
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Let: f(x) = y = 2x − 10 ;

Replace "y" with "x" ; and "x" with "y" ; 

x = 2y − 10 ; 

Now, solve for "y" ; in terms of "x" ;  in "slope-intercept format" ; 

x = 2y − 10 ; 

 ↔  2y − 10 = x ;  

Now, add "10" to each side of the equation ;

     2y − 10 + 10 = x + 10 ; 

to get: 

     2y = x + 10 ; 

Now, divide EACH SIDE of the equation by "2" ; 
   to isolate "y" on one side of the equation; & to solve for "y" in terms of "x" ;

       2y/2 = (x + 10) / 2 ; 

 to get: 

      y = (x + 10)/2 ; 

→  y = (x/2) + (10/2) ; 

→  y = (1/2)x + 5 ; 

Now replace: "y" ; with:  " f ⁻¹(x)"  ;  and rewrite:
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           →   " f ⁻¹(x)  =  x + 5 " .
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Then why is the question on here if you know the answer