\(a,\left(1+x^2\right)^2-4x\left(1-x^2\right)\\ =\left(1+x^2\right)^2-\left(\sqrt{4x\left(1-x^2\right)}\right)^2\\ =\left(1+x^2-\sqrt{4x\left(1-x^2\right)}\right)\left(1+x^2+\sqrt{4x\left(1-x^2\right)}\right)\)
\(b,\left(x^2-8\right)^2-36\\ =\left(x^2-8-6\right)\left(x^2-8+6\right)\\ =\left(x^2-14\right)\left(x^2-2\right)\)
Theo mk là trừ 36 nhé