Question

B2=-9 b3=27 найти первый член

Answer 1

$b_2=-9\; \; ,\; \; b_3=27\; \; \Rightarrow \; \; \; q=\frac{b_3}{b_2}=\frac{27}{-9}=-3\\\\b_2=b_1q\; \; \Rightarrow \; \; b_1=\frac{b_2}{q}=\frac{-9}{-3}=3$

Answer 2

To find the first term of a geometric sequence, we need to know at least two consecutive terms and the common ratio between them.

In this case, we are given two consecutive terms B2 and B3 of a geometric sequence:

B2 = -9 B3 = 27

We can find the common ratio (r) between these terms by dividing B3 by B2:

r = B3 / B2 = 27 / (-9) = -3

Now that we know the common ratio, we can use it to find the first term (B1) of the sequence:

B2 = B1 * r

Substituting the values we know, we get:

-9 = B1 * (-3)

Solving for B1, we get:

B1 = -9 / (-3) = 3

Therefore, the first term of the geometric sequence is 3.