Question

1x2x3x4+1=25=5^2

Answer 1

a(a+1)(a+2)(a+3)+1

=a(a+3)(a+1)(a+2)+1

=(a^2+3a)(a^2+3a+2)+1

=(a^2+3a)^2+2(a^2+3a)+1

=(a^2+3a+1)^2

a(a+1)(a+2)(a+3)+1=(a^2+3a+1 )²

OK啦!