Problems

Find all functions $f(x)$ such that $f(2x+1)=4x^2+14x+7$.

Two different numbers $x$ and $y$ (not necessarily integers) are such that $x^2-2000x=y^2-2000y$. Find the sum of $x$ and $y$.

To each pair of numbers $x$ and $y$ some number $x\ast y$ is placed in correspondence. Find $1993\ast 1935$ if it is known that for any three numbers $x,y,z$, the following identities hold: $x\ast x=0$ and $x\ast (y\ast z)=(x\ast y)+z$.

Prove that for any natural number $a_1>1$ there exists an increasing sequence of natural numbers $a_1,a_2,a_3,\dots$, for which $a_1^2+a_2^2+\cdots +a_k^2$ is divisible by $a_1+a_2+\cdots +a_k$ for all $k\ge 1$.

A numeric set $M$ containing 2003 distinct numbers is such that for every two distinct elements $a,b$ in $M$, the number $a^2+b\sqrt{2}$ is rational. Prove that for any $a$ in $M$ the number $q\sqrt{2}$ is rational.

Solve the equation $(x+1{)}^3=x^3$.

Find $x^3+y^3$ if $x+y=5$ and $x+y+x^{2}y+x{y}^2=24$.

Is it true that, if $b>a+c>0$, then the quadratic equation $a{x}^2+bx+c=0$ has two roots?

Compute the following: $$\frac{(2001\times 2021+100)(1991\times 2031+400)}{{2011}^4}.$$

Solve the inequality: $\lfloor x\rfloor \times \{x\}<x-1$.