book Maths Puzzle Numerical Ability

what is the equation of the parabola with the focus (3,-1)and diretrix y=5

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book Other Question

It takes 10 hours to fill a pool with water, and 20 hours to drain it. If the pool is empty, and the drain is open, how long will it take to fill the pool? use cross products to setermine whether each pair of ratios forms a proportion. is the answer yes or no?
the problem...
7/6,52/48
i cross multiplied but i keep on messing it up