1 .

a)\(A=\frac{2}{2\sqrt[3]{2}+2+\sqrt[3]{4}}\)

b)\(B=\frac{6}{2\sqrt[3]{2}-2+\sqrt[3]{4}}\)

c)C=\(\frac{2}{\sqrt[3]{4}+\sqrt[3]{2}+2}\)

2 .

a)\(A=\sqrt{\sqrt{5}-\sqrt{3-\sqrt{29-12\sqrt{5}}}}\)

b)\(B=\frac{\left(5+2\sqrt{6}\right).\left(49-20\sqrt{6}\right).\sqrt{5-2\sqrt{6}}}{9\sqrt{3}-11\sqrt{2}}\)

c)C=\(\sqrt{4+\sqrt{5\sqrt{3}+5\sqrt{48-10\sqrt{7}+4\sqrt{3}}}}\)

d)D=(\(\left(\sqrt{3}-1\right).\sqrt{6+2\sqrt{2}.\sqrt{3-\sqrt{\sqrt{2}+\sqrt{12}+\sqrt{18-\sqrt{128}}}}}\)

A=x+6x^2+7x^2-6x+1

A=(x^2)^2+2x^2.3x+9x^2-1x^2-6x+7

A=(x^2+3x)^2-2.(x^2+3x).1+1

A=(x^2+3x)^2>=0 với mọi x khi x^2=3x-1=0

A=x+x^2+7x^2-6x+1