令a=2000
则左边=a²+(a+1)²+a²(a+1)²
=[a²-2a(a+1)+(a+1)²]+2a(a+1)+a²(a+1)²
=[a-(a+1)]²+2a(a+1)+a²(a+1)²
=1+2a(a+1)+a²(a+1)²
=[a(a+1)+1]²
=(a²+a+1)²
=右边
令a=2000
则左边=a²+(a+1)²+a²(a+1)²
=[a²-2a(a+1)+(a+1)²]+2a(a+1)+a²(a+1)²
=[a-(a+1)]²+2a(a+1)+a²(a+1)²
=1+2a(a+1)+a²(a+1)²
=[a(a+1)+1]²
=(a²+a+1)²
=右边