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Inequalities
lgx57   0
4 minutes ago
Let $a,b,c,d,e \ge 0$,$\sum \dfrac{1}{a+4}=1$.Prove that:
$$\sum \dfrac{a}{a^2+4} \le 1$$
Let $x,y,z>0$.Prove that:
$$\sum (y+z)\sqrt{\dfrac{yz}{(z+x)(y+x)}} \ge x+y+z$$
0 replies
lgx57
4 minutes ago
0 replies
Find the number of ordered triples (p,q,r)
Darealzolt   2
N 2 hours ago by elizhang101412
Let \(p,q,r\) be prime numbers such that
\[
\frac{1}{pq}+\frac{1}{qr}+\frac{1}{pr}=\frac{1}{839}
\]Hence find the numbers of ordered triples \(\{p,q,r\}\)
2 replies
Darealzolt
2 hours ago
elizhang101412
2 hours ago
Find the sum of all the products a_i a_j
Darealzolt   1
N 2 hours ago by alexheinis
Among the 100 constants \( \{ a_1,a_2,a_3,\dots,a_{100} \} \),there are \(39\) equal to \( -1\), and \(61\) equal to \(1\). Find the sum of all the products \(a_i a_j\) , where \(a \leq i < j \leq 100\).
1 reply
Darealzolt
5 hours ago
alexheinis
2 hours ago
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