a)(t²+t)(t²+t+2)+1, t∈Z
notam x= t²+t
=> x(x+2)+1=x²+2x+1=(x+1) ²
revenim la notatia initiala
=> (x+1) ² =(t²+t+1)² este patrat perfect
b)x(x+1)(x+2)(x+3)+1
x(x+3)(x+1)(x+2)+1=( x²+3x)( x²+3x+2) +1
notam y= x²+3x
=>y(y+2)+1=y ²+2y+1=(y+1) ²
revenim si =>(y+1) ²= (x²+3x+1)² este patrat perfect
