resposta:
Resolução:$\phantom{X}T_{\large k+1}\;=\;\dbinom{n}{k}x^{n-k}y^{k}\phantom{X}$
a)$\phantom{X}T_{\large k+1}\;=\;\dbinom{20}{k}x^{20-k}y^{k}\;{\text com}\;0\leqslant k \leqslant 20\phantom{X}$
oitavo termo:$\phantom{X}T_{\large 7+1}\;=\;\dbinom{20}{7}x^{13}y^{7}\phantom{X}$
b)$\phantom{X}T_8\;=\;77520\,x^{13}\,y^{7}\phantom{X}$
ordem:$\phantom{X}k\,=\,\dfrac{n}{2}\,=\,10\phantom{X}$
c) o termo central é o décimo primeiro termo (11º termo)
$\phantom{X}T_{10+1}\;=\;\dbinom{20}{10}\,x^{10}\,y^{10}\;=\;184\,756\,x^{10}\,y^{10}\phantom{X}$
ordem:$\phantom{X}T_{\large k+1}\;=\;\dbinom{n}{k}x^{n-k}y^{k}\phantom{X}$
$\phantom{X}T_{13}\;=\;\dbinom{20}{12}x^{8}y^{12}\phantom{X}$
$\phantom{X}T_{13}\;=\;\dfrac{\;20!\,x^8\,y^{12}\;}{8!\,12!}\phantom{X}$
d)$\phantom{X}T_{13}\;=\;125970\,x^8\,y^{12}\phantom{X}$
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