Đáp án:a.$A=7\sqrt3$
b.$ B=-3$
Giải thích các bước giải:
a.Ta có:
$A=5\sqrt{3}+\sqrt{27}-3\sqrt{\dfrac13}$
$\to A=5\sqrt{3}+\sqrt{3^3}-\dfrac{3}{\sqrt{3}}$
$\to A=5\sqrt{3}+3\sqrt{3}-\sqrt{3}$
$\to A=(5+3-1)\sqrt{3}$
$\to A=7\sqrt{3}$
b.Ta có:
$B=\dfrac{\sqrt{y^3}-1}{y+\sqrt{y}+1}-\dfrac{y+3\sqrt{y}+2}{\sqrt{y}+1}$
$\to B=\dfrac{(\sqrt{y})^3-1}{y+\sqrt{y}+1}-\dfrac{y+\sqrt{y}+2\sqrt{y}+2}{\sqrt{y}+1}$
$\to B=\dfrac{(\sqrt{y}-1)(y+\sqrt{y}+1)}{y+\sqrt{y}+1}-\dfrac{(\sqrt{y}+2)(\sqrt{y}+1)}{\sqrt{y}+1}$
$\to B=(\sqrt{y}-1)-(\sqrt{y}+2)$
$\to B=-3$
