Question

Допоможіть будь ласочка даю 100 балів ​

Answer 1

Відповідь:фото

Пояснення:

1.

Answer 2

$\displaystyle\bf\\a_{1} =2\\\\a_{2} =5\\\\\\a_{2} =a_{1} +d\\\\d=a_{2} - a_{1} =5-2=3\\\\a_{14} =a_{1} +13d=2+13\cdot3=2+39=41\\\\a_{20} =a_{1} +19d=2+19\cdot3=2+57=59\\\\\\S_{20} =\frac{a_{1} + a_{20} }{2} \cdot 20=(a_{1} + a_{20} )\cdot 10=(2+59)\cdot 10=610\\\\\\Otvet \ : \ a_{14} =41 \ \ , \ \ S_{20} =610$

$\displaystyle\bf\\2)\\\\b_{1} =27\\\\q=\frac{1}{3} \\\\\\b_{5} =b_{1} \cdot q^{4} =27\cdot\Big(\frac{1}{3} \Big)^{4} =27\cdot\frac{1}{81} =\frac{1}{3} \\\\\\S_{4} =\frac{b_{1}\cdot(q^{4} -1) }{q-1} =\frac{27\cdot\Big[\Big(\dfrac{1}{3}\Big)^{4} -1\Big] }{\dfrac{1}{3} -1} =\frac{27\cdot\Big(\dfrac{1}{81} -1\Big)}{-\dfrac{2}{3} } =\\\\\\=\frac{27\cdot\dfrac{80}{81} }{\dfrac{2}{3} } =\frac{27\cdot 80\cdot 3}{81\cdot 2} =40\\\\\\Otvet \ : \ b_{5} =\frac{1}{3} \ \ \ , \ \ \ S_{4} =40$