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 Sep24 awarded Autobiographer Jul14 answered Books on rare techniques Feb14 comment How to solve $x^3 - 2x^2 -16x+16=0$? Wolfram Alpha gives no nice solutions .... Jul14 answered Mathematicians talking about their identity as a person and as a mathematician? Jun7 comment Important numbers in Combinatorics Genocchi numbers: en.wikipedia.org/wiki/Genocchi_number Jun3 comment How can I find the smallest possible of full miles to get full kilometers? What a good idea it was to elaborate the metric system ! May30 answered Pictorial puzzle May17 comment Sum of square root of primes It's A062009 , with no other comment. Mar12 comment Solve $A_n=A_{n-1}+\lfloor \sqrt{A_{n-1}}\rfloor$ Maybe it helps if you see both equalities: $(m+k)^2+m-k+(m+k)=(m+k)^2+2m$ and $(m+k)^2+2m+(m+k)=(m+(k+1))^2+m-(k+1)$ Jul31 comment Given a system of quadratic equations $x^2-a_ix+b_i=0$, can all of the coefficients $a_i$, $b_j$ be solution to one of these above equation? Nice to see you come forward in this nice pb. Do you see now why $\sum {b_i} = 0$ and $\prod{a_i}=1$ come from ? (assuming each $b_i \neq 0$, it can be done without loss of generality after eliminating the solutions $\{x^2 - k_i x = 0 , i=1..n\}$) Don't forget in your study of the permutation on the set of equations, that it's possible to have many intricated cycles. Jul31 comment Given a system of quadratic equations $x^2-a_ix+b_i=0$, can all of the coefficients $a_i$, $b_j$ be solution to one of these above equation? Nice to see you come forward in this nice pb. Jul30 revised Given a system of quadratic equations $x^2-a_ix+b_i=0$, can all of the coefficients $a_i$, $b_j$ be solution to one of these above equation? added 33 characters in body Jul30 answered Given a system of quadratic equations $x^2-a_ix+b_i=0$, can all of the coefficients $a_i$, $b_j$ be solution to one of these above equation? Jul23 comment What will be the value of $P(12)+P(-8)$ if $P(x)=x^{4}+ax^{3}+bx^{2}+cx+d$? And how do you prove that any other value for d gives the same answer ? Jul23 awarded Critic Jul22 comment Roots with equal fractional parts Isn't it, if m = n : $[(x-r)^n-a]-[x^n-b]$. So $r= 0$ and directly $a=b$. Jul11 answered Solve: $|-(x + 1)^2+1|\geq 1$ May26 revised combinatorics: number of options to set a (a,b) ordered pair under terms added 66 characters in body May26 answered combinatorics: number of options to set a (a,b) ordered pair under terms May13 answered What would be a good outdoor maths puzzle for children?