Prove that for all positives $a, b$ and $c$, $(\sum_{cyc}\frac{c + a}{b})^2 \ge 4(\sum_{cyc}ca)(\sum_{cyc}\frac{1}{b^2})$. 
Prove that for all positives $a, b$ and $c$, $$\left(\frac{b + c}{a} + \frac{c + a}{b} + \frac{a + b}{c}\right)^2 \ge 4(bc + ca + ab) \cdot \left(\frac{1}{a^2} + \frac{1}{b^2} + \frac{1}{c^2}\right)$$

Let $ca + ab = m$, $ab + bc = n$ and $bc + ca = p$, we have that $$\left(\frac{m}{a^2} + \frac{n}{b^2} + \frac{p}{c^2}\right)^2 \ge 2(m + n + p) \cdot \left(\frac{1}{a^2} + \frac{1}{b^2} + \frac{1}{c^2}\right)$$
$$\iff \left(\frac{m}{a^2} + \frac{n}{b^2} + \frac{p}{c^2} - 1\right)^2 \ge 2 \cdot \sum_{cyc((m, n, p), (a, b, c))}\left[n \cdot \left(\frac{1}{c^2} + \frac{1}{a^2}\right)\right] + 1$$
Expanding $\displaystyle \sum_{cyc((m, n, p), (a, b, c))}\left[n \cdot \left(\frac{1}{c^2} + \frac{1}{a^2}\right)\right]$ gives $$2 \cdot \sum_{cyc}\frac{ca}{b^2} + \left(\frac{b + c}{a} + \frac{c + a}{b} + \frac{a + b}{c}\right)$$
Let $\dfrac{b + c}{a} = m'$, $\dfrac{c + a}{b} = n'$ and $\dfrac{a + b}{c} = p'$, we have that $$(m' + n' + p' - 1)^2 \ge 2 \cdot \left[2 \cdot \sum_{cyc}\frac{ca}{b^2} + (m' + n' + p')\right] + 1$$
Moreover, $$(m')^2 + (n')^2 + (p')^2 = \sum_{cyc}\left[\left(\frac{c + a}{b}\right)^2\right] \ge 2 \cdot \sum_{cyc}\frac{ca}{b^2}$$
$$\implies (m' + n' + p' - 1)^2 \ge 2 \cdot \left[(m')^2 + (n')^2 + (p')^2 + m' + n' + p'\right] + 1$$
$$\iff -[(m')^2 + (n')^2 + (p')^2] + 2(m'n' + n'p' + p'm') - 4(m' + n' + p') \ge 0$$, which is definitely not correct.
Another attempt, let $(0 <) \ a \le b \le c \implies ab \le ca \le bc \iff ca + ab \le ab + bc \le bc + ca$
$\iff m \le n \le p$ and $a^2 \le b^2 \le c^2 \iff \dfrac{1}{a^2} \ge \dfrac{1}{b^2} \ge \dfrac{1}{c^2}$.
By the Chebyshev inequality, we have that $$3 \cdot \left(\frac{m}{a^2} + \frac{n}{b^2} + \frac{p}{c^2}\right) \le (m + n + p) \cdot \left(\frac{1}{a^2} + \frac{1}{b^2} + \frac{1}{c^2}\right)$$
Any help would be appreciated.
 A: Let $a+b+c=x(a^2+b^2+c^2).$
Thus, $$\sum_{cyc}(a-xa^2)^2\geq0=\left(\sum_{cyc}(a-xa^2)\right)^2$$ or
$$\sum_{cyc}(a^2-2xa^3+x^2a^4)\geq\sum_{cyc}(a^2+2ab)-2x\sum_{cyc}(a^3+a^2b+a^2c)+x^2\sum_{cyc}(a^4+2a^2b^2)$$ or
$$\sum_{cyc}ab-x\sum_{cyc}(a^2b+a^2c)+x^2\sum_{cyc}a^2b^2\leq0.$$ 
Now, let $a^2b^2+a^2c^2+b^2c^2=A$, $\sum\limits_{cyc}ab(a+b)=B$ and $ab+ac+bc=C$.
We proved that there is $x$, id est, $x=\frac{a+b+c}{a^2+b^2+c^2}$ for which $A>0$ and  $$Ax^2-Bx+C\leq0,$$ which gives $$\Delta\geq0$$ or
$$B^2-4AC\geq0$$ or
$$\left(\sum_{cyc}(a^2b+a^2c)\right)^2-4\sum_{cyc}ab\sum_{cyc}a^2b^2\geq0,$$ which is your inequality exactly.
A: WLOG assume $c\neq \text{mid}\{a,b,c\}$. We have:
$$a^2 b^2 c^2 (\text{LHS-RHS}) =\left( a-b \right) ^{2} \left( ab+ca+bc-{c}^{2} \right) ^{2}+4\,ab{c}
^{2} \left( a-c \right)  \left( b-c \right)  \geqq 0$$
Done.
A: We use the standard pqr method.
Let $p = a + b + c, q = ab+bc+ca, r = abc$. The inequality becomes
$$\left(\frac{pq}{r} - 3\right)^2 \ge 4q \left(\left(\frac{q}{r}\right)^2 - 2\frac{p}{r}\right)$$
or (after clearing the denominators)
$$p^2q^2 + 2pqr - 4q^3 + 9r^2 \ge 0.$$
We split into two cases:
1) $p^2 \ge 4q$: Since $p^2q^2 \ge 4q^3$, the inequality is true.
2) $p^2 < 4q$: By Schur's inequality $a^2(a-b)(a-c) + b^2(b-c)(b-a) + c^2(c-a)(c-b) \ge 0$
which is written as $6pr - (4q-p^2)(p^2-q) \ge 0$, we have $r \ge \frac{(4q-p^2)(p^2-q)}{6p}$.
As $p^2 \ge 3q$, we have $r \ge \frac{(4q-p^2)(p^2-q)}{6p}\ge 0$.
Thus, we have 
\begin{align}
&p^2q^2 + 2pqr - 4q^3 + 9r^2\\
\ge\ & p^2q^2 + 2pq \cdot \frac{(4q-p^2)(p^2-q)}{6p} - 4q^3 + 9\left(\frac{(4q-p^2)(p^2-q)}{6p}\right)^2\\
= \ & \frac{(p^2-3q)(3p^2-q)(p^2-4q)^2}{12p^2}\\
\ge \ & 0.
\end{align}
We are done.
A: The inequality follows from the famous inequality Ukraine MO 2001.
If $ a,\,b,\,c$ and $x,\,y,\,z$ non-negative real numbers, then
$$ [x(b+c) + y(c+a) + z(a+b)]^2 \geqslant 4(ab+bc+ca)(xy+yz+zx). \quad (1)$$
Now, using $(1)$ with $x=a^2,\,y=b^2,\,z=c^2$ we get
$$ [a^2(b+c) + b^2(c+a) + c^2(a+b)]^2 \geqslant 4(ab+bc+ca)(a^2b^2+b^2c^2+c^2a^2),$$
or
$$\left(\frac{b + c}{a} + \frac{c + a}{b} + \frac{a + b}{c}\right)^2 \geqslant 4(ab+bc+ca)\left(\frac{1}{a^2} + \frac{1}{b^2} + \frac{1}{c^2}\right).$$
Note. The sum of squares by Darij Grinberg
$$[ab(a+b)+bc(c+a)+ca(c+a)]^2-4(ab+bc+ca)(a^2b^2+b^2c^2+c^2a^2)$$
$$=\sum a^2b^2(a-b)^2 + \sum 2abc \sum a(a-b)(a-c).$$
A: A NOTE
The given inequality
$$
\left(\sum_{cyc}\frac{a+b}{c}\right)^2\geq 4\left(\sum_{cyc}ab\right)\left(\sum_{cyc}\frac{1}{a^2}\right)\textrm{, }a,b,c>0\tag 1
$$
is written as
$$
\left(\sum_{cyc}ab(a+b)\right)^2\geq4\left(\sum_{cyc}ab\right)\left(\sum_{cyc}a^2b^2\right).\tag 2
$$
Hence if $s=a+b+c$ and $p=abc$ and $s_h=\frac{1}{a}+\frac{1}{b}+\frac{1}{c}$, then
$$
\left(\sum_{cyc}ab(a+b)\right)^2=p^2(ss_h-3)^2
$$
and
$$
4\left(\sum_{cyc}ab\right)\left(\sum_{cyc}a^2b^2\right)=4p^3s_h(s_h^2-2s/p)
$$
Hence (2) becomes
$$
9+2ss_h+s^2s_h^2-4ps_h^3\geq 0.\tag 3
$$
Inequality (3) is a equivalent to
$$
9\leq ss_h\leq \rho\left(\frac{4p}{s^3}\right),
$$
where $\rho=\rho(t)$ is the real root of
$$
t \rho^3=9+2 \rho+\rho^2.
$$
Hence given positive numbers $a,b,c$ we have
$$
9\leq (a+b+c)\left(\frac{1}{a}+\frac{1}{b}+\frac{1}{c}\right)\leq x,
$$
where $x$ is the real root of
$$
9+2x+x^2=\frac{4abc}{(a+b+c)^3}x^3.
$$
