In the complex number system, what is the value of the expression $10i^4-4i^2-2$ ? (Note: $i=\sqrt{-1})$

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The first few powers of $i$:

$$i=\sqrt{-1}$$ $$i^2=(\sqrt{-1})^2=-1$$ $$i^4 = (i^2)^2 =(-1)^2 =1$$

Therefore,

$$10i^4-4i^2-2$$ $$10(1)-4(-1)-2$$ $$10+4-2$$ $$= \boxed{12}$$