a)27x³+27x²+9x+1
=(3x)³+3.(3x)².1+3.3x.1²+1³
=(3x+1)³
b)x³+$x^{3}$ +3$\sqrt[]{2}$$x^2$y+6xy+ 2$\sqrt[]{2}$$y^3$ =$x^{3}$ +3$\sqrt[]{2}$$x^2$y+6xy+ 2$\sqrt[]{2}$$y^3$
=$x^{3}$+3x²$\sqrt[]{2}$y+3.x.2y²+($\sqrt[]{2}$)³$y^3$
=$x^{3}$+3x²$\sqrt[]{2}$y+3.x.($\sqrt[]{2}$)²$y²+$4($\sqrt[]{2}$)³$y^3$
=(x+$\sqrt[]{2}$y)³