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b) conţine a^2 in dezvoltarea​

B Conţine A2 In Dezvoltarea class=

Răspuns :

[tex]\it T_{k+1}=C^k_{15}(x^{\frac{2}{3}})^{15-k}\cdot(xa^\frac{2}{3})^k\\ \\ a^{\frac{2k}{3}}=a^2 \Rightarrow\dfrac{2k}{3}=2|_{:2}\Rightarrow \dfrac{k}{3}=1 \Rightarrow k=3[/tex]