Giải thích các bước giải:
ĐK: $x≤1$
$\sqrt[]{(1+x)^3}+$ $\sqrt[]{(1-x)^3}$
$=\frac{[\sqrt[]{(1+x)^3}+ \sqrt[]{(1-x)^3}].[\sqrt[]{(1+x)^3}-\sqrt[]{(1-x)^3}]}{\sqrt[]{(1+x)^3}-\sqrt[]{(1-x)^3}}$
$=\frac{(1+x)^3-(1-x)^3}{\sqrt[]{(1+x)^3}-\sqrt[]{(1-x)^3}}$
$=\frac{(1+3x+3x^2+x^3)-(1-3.x+3x^2+x^3)}{\sqrt[]{(1+x)^3}-\sqrt[]{(1-x)^3}}$
$=\frac{6x}{(1+x)\sqrt[]{(1+x)}-(1-x)\sqrt[]{(1-x)}}$
