Answer
FALSE
Work Step by Step
FALSE
for example $x=2$
and the function, $f(x) = x^2$
$f(3\times x)=f(3\times 2)=f(6)=6^2=36$
and
$3\times f(x)=3\times f(2)= 3\times 2^2=3\times4=12$
It disproves the statement.
$f(3x)\ne 3f(x)$
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