- Hướng dẫn giải

Ta có:

 $$\begin{gathered} 4b^2{c}^2 - {\left(c^2+b^2-a^2\right)}^2 \\ ={\left(2bc\right)}^2-{\left(c^2+b^2-a^2\right)}^2 \\ =\left(2bc+ c^2+b^2-a^2\right)\left(2bc-c^2-b^2+a^2\right) \\ =\left[{\left(b+c\right)}^2-a^2\right]\left[a^2-\left(b^{2 }- 2bc +c^2\right)\right] \\ =\left[{\left(b+c\right)}^2-a^2\right]\left[a^2-{\left(b-c\right)}^2\right] \\ =\left(b+c+a\right)\left(b+c-a\right)\left(a+b-c\right)\left(a-b+c\right) \end{gathered}$$  

Đáp án cần chọn là : A