Question

) Determine o 5º termo da PG ,
a) (2, 4,...)
b) ( -3, -6,…)
c) ( 4, -8,…)

Answer 1

Explicação passo-a-passo:

a)

• Razão

$\sf q=\dfrac{a_2}{a_1}$

$\sf q=\dfrac{4}{2}$

$\sf q=2$

• 5° termo

$\sf a_n=a_1\cdot q^{n-1}$

$\sf a_5=a_1\cdot q^4$

$\sf a_5=2\cdot2^4$

$\sf a_5=2\cdot16$

$\sf a_5=32$

b)

• Razão

$\sf q=\dfrac{a_2}{a_1}$

$\sf q=\dfrac{-6}{-3}$

$\sf q=2$

• 5° termo

$\sf a_n=a_1\cdot q^{n-1}$

$\sf a_5=a_1\cdot q^4$

$\sf a_5=(-3)\cdot2^4$

$\sf a_5=(-3)\cdot16$

$\sf a_5=-48$

c)

• Razão

$\sf q=\dfrac{a_2}{a_1}$

$\sf q=\dfrac{-8}{4}$

$\sf q=-2$

• 5° termo

$\sf a_n=a_1\cdot q^{n-1}$

$\sf a_5=a_1\cdot q^4$

$\sf a_5=4\cdot(-2)^4$

$\sf a_5=4\cdot16$

$\sf a_5=64$