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deonstrati ca numarul n=2012*2013*2014*2015+1este patrat perfect

Răspuns :

demonstram ca x(x+1)(x+2)(x+3)+1 este patrat perfect.
x(x+1)(x+2)(x+3)+1=x(x+3)×(x+1)(x+2)+1=(x²+3x)(x²+3x+2)+1=
=(x²+3x)(x²+3x)+2(x²+3x)+1²=(x²+3x)²+2(x²+3x)+1²
=(x²+3x+1)²
x(x+1)(x+2)(x+3)+1=(x²+3x+1)²
Pentru x=2012 obtinem:
2012*2013*2014*2015+1=(2012²+3·2012+1)²