(a2−2)(a2+2)−(2−a2)2

[latex]( a^{2}-2 ) ( a^{2} +2 ) - ( 4 - 4a + (a^{2} ) ^{2} ) = ( a^{2}-2 ) ( a^{2} +2 )- (4-4a+ a^{4} )[/latex] = [latex]( a^{2} -2 ) ( a^{2} + 2) - 4 + 4a - a^{4} = a^{4}+ 2a^{2} - 2a^{2} - 4 -4 +4a - a^{4} [/latex] = 4a -8