Question 146
Find the minimal value of
$$
\frac{(a^2 + b^2 + 2c^2 + 3d^2)(2a^2 + 3b^2 + 6c^2 + 6d^2)}{(a+b)^2(c+d)^2}
$$
where $a, b, c, d$ are positive real numbers.
$$
\frac{(a^2 + b^2 + 2c^2 + 3d^2)(2a^2 + 3b^2 + 6c^2 + 6d^2)}{(a+b)^2(c+d)^2}
$$
where $a, b, c, d$ are positive real numbers.