5(a+1)²-8(a+1)(a-1)+3(a-1)²
=5(a²+2a+1)-8(a²-1)+3(a²-2a+1)
=(5-8+3)a²+(10-6)a+5+8+3
=4a+16
=4×1/4+16
=17
祝学习快乐