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Nicoleta2023
a fost răspuns

x-y=15
x²-y²=75
x+y=? ​

Răspuns :

Ancahaldan27
(x+y)(x-y)=x^2-y^2
(x+y) * 15 = 75
(x+y) = 75:15
(x+y) = 5
Targoviste44

[tex]\it x-y=15\ \ \ \ \ (*)\\ \\ x^2-y^2=75\ \Rightarrow (x-y)(x+y)=75 \stackrel{(*)}{\Longrightarrow}\ 15\cdot(x+y)=75|_{:15} \Rightarrow x+y=5[/tex]