<s>[INST] PEMDAS question: $F(x) = 3x^2 - x+2$. Find $[f(a)]^2$ How should I go about doing this? $(3a^2-a+2)^2$? 
Thus, $9a^4-a^2+4$
 [/INST] Hint For any real numbers $x,y$ we have $$\color{green}{(x-y)^2 = x^2-2xy+y^2}, \quad \color{blue}{(x+y)^2 = x^2+2xy+y^2},$$
and note that with $\color{green}{x = (2-a)}$ and $y = 3a^2$ we get 
$$(3a^2-a+2)^2=\color{blue}{(x+y)^2} = \ldots$$
Can you continue from here?
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