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Răspuns:
x=8
Explicație pas cu pas:
Se foloseste formula
1+3+5+...+(2x-1)=x²
1+3+5+...+(2x-1)=15²=>
2x-1=15
2X=15+1
2x=16
x=16:2
x=8
[tex]\it 1+3+5+\ ...\ +(2x-1)=64 \Rightarrow x^2=64 \Rightarrow x^2=8^2 \Rightarrow x=8\\ \\ \\ 1+3+5+\ ...\ +(2x-1)=225 \Rightarrow x^2=225 \Rightarrow x^2=15^2 \Rightarrow x=15[/tex]