Mathematics: The arithmetic sequence ai is defined by the formula: a 1 =15 a i =a i-1 -7 Find the sum of the first 660 terms in the sequence.

The arithmetic sequence ai is defined by the formula:

victoriapellam04

17.03.2022

The sum of the first 660 terms in the sequence=−1512390

Step-by-step explanation:

We are given that an arithmetic sequence

a_1=15

$a_{i}=a_{i-1}-7$

We have to find the sum of first 660 terms

Substitute i=2

a_2=a_1-7=15-7=8

Substitute i=3

a_3=a_2-7=8-7=1

Now, the common difference

d=a_2-a_1=8-15=-7

Now, sum of n terms of an A.P

$S_n=\frac{n}{2}(2a+(n-1)d)$

Substitute n=660, d=-7, a=15

$S_{660}=\frac{660}{2}(30+(660-1)(-7))$

$S_{660}=-1512390$

Hence, the sum of the first 660 terms in the sequence=−1512390

0,0(0 оценок)

stephb1369

24.09.2021

Area of the rectangle = ( x²+12x+27)unit²

Step-by-step explanation: Length = x+3 Breadth = x+9

∴ Area of Rectangle = L×B

(x+3)(x+9) = x²+9x+3x+27 = (x²+12x+27) unit²

0,0(0 оценок)