Question

А1 = -4, а5 = 6, S5 = ?​

Answer 1

Объяснение:

По формуле S= a1+an/2 *n.

S5= -4 + 6 / 2 * 5 = 2/2 * 5/1 = 1*5 = 5 .

Ответ : 5 .

Answer 2

It seems like you are dealing with an arithmetic sequence, where "а1" represents the first term, "а5" represents the fifth term, and "S5" represents the sum of the first 5 terms.

To find the sum of the first 5 terms of an arithmetic sequence, you can use the following formula:

S_n = n/2 * [2a_1 + (n-1)d]

Where:

• S_n is the sum of the first n terms.
• n is the number of terms you want to find the sum for.
• a_1 is the first term of the sequence.
• d is the common difference between the terms.

In your case:

• a_1 = -4 (the first term)
• a_5 = 6 (the fifth term)
• n = 5 (we want to find the sum of the first 5 terms)

We need to find the common difference (d) first, which can be calculated using the given terms:

d = (a_5 - a_1) / (5 - 1) = (6 - (-4)) / 4 = (6 + 4) / 4 = 10 / 4 = 2.5

Now that we have the common difference, we can find S_5:

S_5 = 5/2 * [2*(-4) + (5-1)2.5] S_5 = 5/2 * [-8 + 42.5] S_5 = 5/2 * [-8 + 10] S_5 = 5/2 * 2 S_5 = 5

So, the sum of the first 5 terms of this arithmetic sequence is 5.