For question $3,$ you must use a proof by contradiction:

$$ First give the claim that you will assume true and from which you will

derive a contradiction.

$$ Use the definition of order to write the inequality from which you will

derive the contradiction.

$$ Simplify the inequality and explain how you derive a contradiction from

it$\mathrm{.}3.(2$ marks$)$ Use the definition of $$big Oh$$ to prove that $4$n

is not O$(2$n

$)$