Answer: x = 4
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Step-by-step explanation:
Replace f(x) with 0 and solve for x.
f(x) = 3x-12
0 = 3x-12
3x-12 = 0
3x = 12
x = 12/3
x = 4 is a zero, aka root, of the function
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Check:
f(x) = 3x-12
f(4) = 3(4)-12
f(4) = 12-12
f(4) = 0
The answer is confirmed.