Solve for a. 25=a2+b2 a: a=5−b or a=5+b b: a=25−b^2 c: a=±25−b^2−−−−−−√ d: a=±25+b2−−−−−−√

The correct answer is:  [C]:  " a =  ±  " .
___________________________________________________________
Explanation:
_________________________________________________________
We are given:  
_________________________________________________________
    →   "  25  =  a²  +  b²  "  ;   Solve for "a" ; 
_________________________________________________________

    →  To solve for "a" ;  we want to isolate "a" on one side of the equation.
_________________________________________________________
We can rewrite:  "  25  =  a²  +  b²  "  ;

as:  " a²  +  b²  = 25 " .

_________________________________________________________
Then, we can subtract " b² "  from each side of the equation; as follows:
_________________________________________________________

   →  " a²  +  b²  −  b²  =  25 − b²  "  ;

to get:
_________________________________________________________
   →  " a²  =  25 − b²  "  ;
_________________________________________________________
  →  Now,  take the square root of EACH SIDE of the equation ; 
to isolate "a" on one side of the equation; & to solve for the value(s) of "a" ; 
_________________________________________________________

  →  √(a²)  =   ;

to get:
_____________________________________________________
  →    a   =  | |  ;

  →    a   =  ±   ; 
  
  →  which is:  Answer choice:  [C]:  " a =  ±    " .
______________________________________________________