Câu a, Rút gọn:
\(B=\sqrt{\left(a^2+\dfrac{4}{a^2}\right)^2-8\left(a^2+\dfrac{2}{a^2}\right)^2+48}\)
\(\Leftrightarrow\sqrt{\left(\dfrac{a^4+4}{a^2}\right)^2-8.\left(\dfrac{a^4+2}{a^2}\right)+48}\)
\(\Leftrightarrow\sqrt{\dfrac{\left(a^4+4\right)^2}{a^4}-\dfrac{8\left(a^4+2\right)^2}{a^4}+48}\)
\(\Leftrightarrow\sqrt{\dfrac{\left(a^4+4\right)^2-8\left(a^4+2\right)^2}{a^4}+48}\)
\(\Leftrightarrow\sqrt{\dfrac{\left(a^4+4\right)^2-8\left(a^4+2\right)^2+48a^4}{a^4}}\)
\(\Leftrightarrow\sqrt{\dfrac{a^8+8a^4+16-8\left(a^8+4a^4+4\right)+48a^4}{a^4}}\)
\(\Leftrightarrow\sqrt{\dfrac{a^8+8a^4+16-8a^8-32a^4-32+48a^4}{a^4}}\)
\(\Leftrightarrow\sqrt{\dfrac{-7a^8+42a^4-16}{a^4}}\)
\(\Leftrightarrow\)\(\dfrac{\sqrt{-7a^8+24a^4-16}}{a^2}\)
