Answer:
x  3
 3
Step-by-step explanation:
if  x = 3 then  the rational expression    4 / (x - 3) is undefined
because we get   4/0 = undefined .
 
        
             
        
        
        
Answer:
-2n - 12
Step-by-step explanation:
Combine like terms. Note that each term has one variable (n). Also note  that one negative sign and one positive sign results in a negative sign.
-6n + (-12) + 4n = -6n  + 4n - 12 = -2n - 12
-2n - 12 is your answer
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U can use  real world numbers and problems to help