\[\left( a^{\frac{1}{2}} - a^{\frac{1}{4}} \right)\left( a^{\frac{1}{4}} + 1 \right)\left( a^{\frac{1}{4}} + a^{- \frac{1}{4}} \right) =\]
\[= \left( a^{\frac{1}{4}} - 1 \right)\left( a^{\frac{1}{4}} + 1 \right)\left( a^{\frac{1}{2}} + 1 \right) =\]
\[= \left( \left( a^{\frac{1}{4}} \right)^{2} - 1 \right)\left( a^{\frac{1}{2}} + 1 \right) =\]
\[= \left( a^{\frac{1}{2}}–1 \right)\left( a^{\frac{1}{2}} + 1 \right) =\]
\[= \left( a^{\frac{1}{2}} \right)^{2} - 1 = a - 1\]
\[a = 41:\]
\[a - 1 = 41 - 1 = 40.\]