Problems

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On the \(xy\)-plane shown below is the graph of the function \(y=ax^2 +c\). At which points does the graph of the function \(y=cx+a\) intersect the \(x\) and \(y\) axes?

Does there exist a natural number which, when divided by the sum of its digits, gives a quotient and remainder both equal to the number 2011?

In six baskets there are pears, plums and apples. The number of plums in each basket is equal to the total number of apples in the other baskets. The number of apples in each basket is equal to the total number of pears in the other baskets. Prove that the total number of fruits is divisible by 31.

Suppose that: \[\frac{x+y}{x-y}+\frac{x-y}{x+y} =3.\] Find the value of the following expression: \[\frac{x^2 +y^2}{x^2-y^2} + \frac{x^2 -y^2}{x^2+y^2}.\]

After a circus came back from its country-wide tour, relatives of the animal tamer asked him questions about which animals travelled with the circus.

“Where there tigers?”

“Yes, in fact, there were seven times more tigers than non-tigers.”

“What about monkeys?”

“Yes, there were seven times less monkeys than non-monkeys.”

“Where there any lions?”

What is the answer he gave to this last question?