Guys Help! thx! Show that the polynomial f(x)=2x+1 has a multiplicative inverse in Z_4 [x].
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$\displaystyle \left[f(x)\right]^2=(2x+1)^2=4x^2+4x+1=1$ in $\displaystyle \mathbb Z_4[x].$ So $\displaystyle f(x)$ is its own inverse in $\displaystyle \mathbb Z_4[x].$
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