bài 1.
$A=\sqrt{a^{2}+4ab^{2}+4b^{4}}-\sqrt{4a^{2}-12ab^{2}+9b^{4}}$
$=\sqrt{\left ( a+2b^{2} \right )^{2}}-\sqrt{\left ( 2a-3b^{2} \right )^{2}}$
$=|a+2b^{2}|-|2a-3b^{2}|$
$=|\sqrt{2}+2.1^{2}|-|2\sqrt{2}-3.1^{2}|$
$=\sqrt{2}+2-3+2\sqrt{2}=3\sqrt{2}-1$