Final answer:
When x = -6, the rational expression (x^2-4x)/(2x+4) evaluates to -7.5 after substituting -6 into the expression and simplifying the resulting fraction.
Step-by-step explanation:
To find the value of the rational expression (x^2-4x)/(2x+4) for x=-6, firstly substitute x with -6 in the expression.
Substitution: ((-6)^2 - 4(-6)) / (2(-6) + 4) = (36 + 24) / (-12 + 4) = 60 / -8
Now, simplify the fraction to get the final value:
60 / -8 = -7.5
Thus, for x = -6, the value of the expression is -7.5.