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For questions about algebra and precalculus topics, which include linear, exponential, logarithmic, polynomial, rational, and trigonometric functions; conic sections, binomial, surds, graphs and transformations of graphs, solving equations and systems of equations; and other symbolic manipulation topics.

2 votes
2 answers
117 views

Let $x, y\in \mathbb{R}$, solve the following system: $\begin{cases}x^9+y^9=1\\x^{10}+y^{10}...

Let $x, y\in \mathbb{R}$, solve the following system: $$\begin{cases}x^9+y^9=1\\x^{10}+y^{10}=1 \end{cases}$$ I have tried to use notations, $S = x+y$ and $P=xy$, but I couldn't continue because of t …
David399's user avatar
  • 301
7 votes
4 answers
246 views

Prove that the equation $x^4-4x^3-14x^2-4x+1=0$ has a root $x = \tan 9^\circ$

Prove that the equation $x^4-4x^3-14x^2-4x+1=0$ has a root $x = \tan 9^\circ$. I have tried calculating $\tan 9^\circ$ and substituting it in the equation but it is pretty tough to calculate that. Can …
David399's user avatar
  • 301
0 votes
1 answer
70 views

Find the maximum value of $|b|+|c|$.

Let $\mathit{f}:\mathbb{R}\to\mathbb{R}$, $\mathit{f}(x)=ax^2+bx+c$ such that $|\mathit{f}(x)|\le1$ for any $x\in\mathbb{R}$ with $|x|\le1$. Find the maximum value of $|b|+|c|$. I presume that if $x=0 …
David399's user avatar
  • 301
1 vote
1 answer
42 views

Given any $a,b,c \geq 1$, prove that $a^2 + b^2 + c^2 \geq 2a\sqrt{b-1} + 2b\sqrt{c-1} + 2c\...

Given any $a,b,c \geq 1$, prove that: $a^2 + b^2 + c^2 \geq 2a\sqrt{b-1} + 2b\sqrt{c-1} + 2c\sqrt{a-1}$ I tried using most of the popular inequalities and I didn't end up anywhere. Can anyone guide me …
David399's user avatar
  • 301