Question

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Answer 1

$f(x)=8x^2-4x\\\\\text{substitute}\ x=\dfrac{m}{4}\\\\f\left(\dfrac{m}{4}\right)=8\cdot\left(\dfrac{m}{4}\right)^2-4\cdot\dfrac{m}{4}=8\cdot\dfrac{m^2}{16}-m=\dfrac{m^2}{2}-m$

$\text{Answer:}\ D.\ \dfrac{m^2}{2}-m$