Question

ambele ex daca se poate va rog

Answer 1

Răspuns:

Explicație pas cu pas:

19.

an = a1 + (n - 1)r

a1 = 4

r = -1

n = 30

a30 = 4 + (30 - 1)*(-1) = 4 + 29*(-1) = 4 - 29 = -25

20.

q = 3

b2 = 3

b3 = b2*q = 3*3 = 9

b4 = b3*q = 9*3 = 27

b5 = b4*q = 27*3 = 81

Answer 2

$19.~~a_1=4,~r=-1,~a_{30}=?\\\\ a_n=a_1+(n-1) \cdot r\\\\ a_{30}=a_1+(30-1) \cdot r=4+29 \cdot (-1)=4-29=-25$

$20.~~b_2=3,~q=3,~b_5=?\\\\ b_n=b_1 \cdot q^{n-1}\\\\ b_2=3 \Rightarrow b_1\cdot q^{2-1}=3 \Rightarrow b_1 \cdot q=3 \Rightarrow b_1 \cdot 3=3 \Rightarrow b_1=1\\\\ b_5=b_1 \cdot q^{5-1}\Rightarrow b_5=b_1 \cdot q^4 \Rightarrow b_5=1 \cdot 3^4 \Rightarrow b_5=81$