If y varies directly as the square of x, that means that y=k*x^2. Plugging y=100 and x=5 into it, we get 100=k*5^2=k*25. Dividing by both sides, we get k=100/25=4. Going back to the original equation, we now know that y=4*x^2. Plugging 9=x in, we get 4*9^2=4*81=324=y
Answer:

Step-by-step explanation:
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Given:

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Collect like terms.

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Simplify

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