Răspuns :
[tex]a = 2^{1988} ( 2^{2} - 2-1 ) = 2^{1988} (4-2-1)= 2^{1988} \\
0,25 = 25/100= 1/4 = \frac{1}{ 2^{2} } = 2^{-2} \\
4^{993} = [ 2^{2} ]^{993} = 2^{1986} \\
\frac{a}{x} = \frac{ 2^{1988} }{x} = \frac{ 2^{1986} }{ 2^{-2} } \\
x = ( 2^{1988} ori 2^{-2} ) : 2^{1986} = 2^{1986} : 2^{1986} = 1[/tex]