Question

①1乘2乘3乘4加1=5的平方=（1的平方加3乘1加1）的平方

Answer 1

n(n+1)(n+2)(n+3)+1

=[n(n+3)][(n+1)(n+2)]+1

=(n^2+3n)[(n^2+3n)+2]+1

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

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