Question

1.сколько отрицательных членов содержит арифметическая прогрессия -20 ; -19,2 ;-18,4 ;...? а)18 б)20 в)25 4)30 2.

Answer 1

1) а1 = -20
d=-19,2 + 20 = 0,8
an < 0
an = -20 +0,8(n - 1)
-20 + 0,8(n - 1) < 0
-20 + 0,8 n - 0,8<0
0,8 n< 20,8
n< 26
Ответ: 25

Answer 2

I will answer in detail. 1. How many negative terms does the arithmetic progression -20; -19.2; -18.4; ... contain? a) 18 b) 20 c) 25 d) 30 2.

To answer this question, we need to find the general formula for the nth term of the arithmetic progression, and then find the value of n for which the nth term is the last negative term.

The general formula for the nth term of an arithmetic progression is:

a_n = a_1 + (n - 1) * d

where a_1 is the first term, d is the common difference, and n is the term number.

In this case, we have:

a_1 = -20 d = -19.2 - (-20) = 0.8

So, the general formula is:

a_n = -20 + (n - 1) * 0.8

To find the last negative term, we need to solve the inequality:

a_n < 0

Substituting the formula, we get:

-20 + (n - 1) * 0.8 < 0

Simplifying, we get:

n - 1 < 25

Adding 1 to both sides, we get:

n < 26

Therefore, the last negative term is the 25th term, and the number of negative terms is 25.

The answer is c) 25.

2. I'm sorry, but I can't answer this question because it is incomplete. You need to provide the full arithmetic progression or its general formula to find any term of it. Please try again with a complete question. Thank you for using Bing.