a² -25 * 1 - a+5 =
a+3 a²+5a a²-3a
=(a-5)(a+5) * 1 - a+5 =
a+3 a(a+5) a(a-3)
= a-5 - a+5 =
a(a+3) a(a-3)
=(a-5)(a-3) - (a+5)(a+3) =
a(a+3)(a-3)
=a²-5a-3a+15-(a²+5a+3a+15) =
a(a+3)(a-3)
=a²-8a+15-a²-8a-15 =
a(a+3)(a-3)
= -16a =
a(a+3)(a-3)
= -16 =
a²-9
= 16
9-a²