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★ 7/10

Square Values of a Quadratic

The quadratic f(x)=x2+bx+cf(x) = x^2 + bx + c passes through (1,13)(1, 13), and y=f(x−12)y = f\left(x - \tfrac12\right) is even.

1. Find f(x)f(x). 2. Are there points on y=f(x)y = f(x) whose xx-coordinate …

functionsQuadratic EquationsDiophantine Equationsnumber theory+1
★ 8/10

A Chord and a Diameter

Consider the ellipse G ⁣:x22+y2=1G \colon \dfrac{x^2}{2} + y^2 = 1. A line ll through the left focus FF, not lying along the xx-axis, meets GG at AA and BB; let MM be the midpoint of …

Power of a Pointconic sectionsanalytic geometrySymmetry
★ 9/10

A Functional Equation Hunt

Find all functions f ⁣:R→Rf \colon \mathbb{R} \to \mathbb{R} satisfying

f(f(x+y))=f(x+y)+f(x)f(y)−xyfor all x,y∈R.f(f(x+y)) = f(x+y) + f(x)f(y) - xy \qquad \text{for all } x, y \in \mathbb{R}.
functionsSubstitutionalgebraFunctional Equations
★ 6/10

A Ratio of Distances, Minimized

The distance from the point M(3,2)M(3, 2) to the directrix of the parabola C ⁣:y=ax2C \colon y = ax^2 (with a>0a > 0) is 44. Let FF be the focus of the parabola, let N(1,1)N(1, 1), and let PP m…

Extremaconic sectionsanalytic geometry
★ 7/10

A Sliding Equilateral Triangle and a Dot Product

figure

As shown in the figure, an equilateral triangle ABCABC has side length 22. Its vertices BB and CC move along the…

plane geometrytrigonometryExtremaParametrization+2
★ 7/10

A Linear Coefficient Product

The function f(x)=ax+bf(x) = ax + b satisfies ∣f(x)∣⩽1|f(x)| \leqslant 1 for all x∈[0,1]x \in [0, 1]. Find the range of possible values of (a+1)(b+1)(a+1)(b+1).

functionsLinear ProgrammingAM-GMinequality
★ 8/10

Two Roots in a Moving Window

Suppose the equation

∣x−k∣=22 kx|x-k|=\frac{\sqrt 2}2\,k\sqrt x

has two distinct real roots in the interval [k−1,k+1][k-1,k+1]. Find the range of the real number kk.

functionsAbsolute ValueMonotonicityCasework
★ 7/10

Taxicab Betweenness

For points A(x1,y1)A(x_1, y_1) and B(x2,y2)B(x_2, y_2) in the coordinate plane, define the taxicab distance

d(A,B)=∣x2−x1∣+∣y2−y1∣.d(A, B) = |x_2 - x_1| + |y_2 - y_1|.

Fix two distinct points AA and BB.

1…

plane geometryfunctionsAbsolute ValueCasework
★ 9/10

A Forced Large Gap

Find the largest positive integer nn with the property: however the numbers 11 through 400400 are placed into a 20×2020 \times 20 grid, some row or column contains two numbers differ…

combinatoricsPigeonholeAM-GM
★ 8/10

One Max, One Min in a Window

The function

f(x)=mx+sin⁡xexf(x) = mx + \frac{\sin x}{e^x}

has exactly one local maximum and one local minimum on (0,2π)(0, 2\pi). Find the range of possible values of the real number mm.

ExtremacalculusMonotonicityCasework
★ 6/10

Largest Planar Cross-Section of a Unit Cube

figure

A cube has edge length 11. Among all planes that cut the cube, find the maximum possible area of the resulting cross-secti…

Extremasolid geometryCasework
★ 6/10

An Eighth Derivative at Zero

Let f(x)=esin⁡(x2)f(x) = \mathrm{e}^{\sin(x^2)}. Find f(8)(0)f^{(8)}(0).

calculusBinomial Theorem

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