A) - (a-5)(a+3)-(1-a)^2= - (a^2+3a-5a-15)- (1-2a+a^2) =
- (a^2 -2a+15 )-(1-2a+a^2)= - a^2 +2 a - 15 -1+2a -a^2 =
-2a^2 + 4a -16= -2 ( a^2 -2 a +8 )
C ) ( 2 a+ 0.5)^2 - ( 0.5 - 2 a )^2 = ( 0.5 + 2 a )^2 - ( 0 . 5 - 2 a )^2=
0.25 +2 a + 4 a ^2 - 0.25+ 2 a - 4 a^2= 4 a .
e ) 25 x ^2 +( 7+5 x) (7-5x )= 25x^2 + 49-25x^2=49