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determina numarul natural n care verifica egalitatea (n×n)-n=600

Răspuns :

(n×n)-n=600
n²-n-600=0
a=1
b=-1
c=-600
Δ=(-1)²+4×1×(-600)=1+2400=2401
n₁=(1+√2401)/2=(1+49)/2=25                 25∈N
n₂=(1-√2401)/2=(1-49)/2=-24                 -24∈Z nu este solutie 

verificare
25(25-1)=25×24=600