(f+g-k)(x) means to add the equations f(x) and g(x) then subtract k(x)
2x^2 + 3x + 4x - 9 = 2x^2 +7x -9
2x^2 + 7x - 9 - x^2 -7x = x^2 -9
The answer is : x^2 - 9
 
        
                    
             
        
        
        
An expression is defined as a set of numbers, variables, and mathematical operations. The correct options are A and C.
<h3>What is an Expression?</h3>
In mathematics, an expression is defined as a set of numbers, variables, and mathematical operations formed according to rules dependent on the context. 
The given exponential (6⁻¹⁰/6⁻⁴) function can be simplified as shown below,
(6⁻¹⁰/6⁻⁴)
 = 6⁻¹⁰ × 6⁴
 = 6⁽⁻¹⁰⁺⁴⁾
 = 6⁻⁶
 = 1/6⁶
Hence, the correct options are A and C.
Learn more about Expression:
brainly.com/question/13947055
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Answer:
Not a function because it does not pass the Vertical Line Test.