Question

Sa se rezolve ecuatia

Answer 1

uite. si tine minte regula de sus de pe primul rand

Answer 2

n(n-1)/2=n+2

n(n-1)=2(n+2)

n²-n=2n+4

n²-n-2n-4=0

n²-3n-4=0

Δ=b²-4ac=3²+16=9+16=25 >0

n₁=(3+5)/2=8/2=4 ∈ N

n₂=(3-5)/2=-2/2=-1 ∉ N

n=4 ∈ N