$P=4(\frac{a}{b+c-a}+\frac{1}{2})+9(\frac{b}{c+a-b}+\frac{1}{2})+16(\frac{c}{a+b-c}+\frac{1}{2})-\frac{29}{2}$$P=\frac{a+b+c}{2}.(\frac{4}{b+c-a}+\frac{9}{c+a-b}+\frac{16}{a+b-c})-\frac{29}{2}$
$\Rightarrow P\geq \frac{a+b+c}{2}.\frac{(2+3+4)^2}{(b+c-a)+(c+a-b)+(a+b-c)}-\frac{29}{2}$
$\Rightarrow P\geq \frac{81}{2}-\frac{29}{2}=26$
Dấu = xảy ra khi $\frac{a}{7}=\frac{b}{6}=\frac{c}{5}$