four cards numbered 1, 5, 8, and 9 are placed in a bag. A card is drawn at random and then replaced. Then a card is drawn at ran
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Divide both sides by -3, and replace with
. Then
Factorize the quadratic in to get
which in turn means
But for all real
, so we can ignore the first solution. This leaves us with
If we allow for any complex solution, then we can continue with the solution we ignored: