Question

The sum of first 15 term of AP is 10 , 6, 2 ....is

Answer 1

Answer:

-270

Step-by-step explanation:

hope it will help u.....

Answer 2

To find:-

• Sum of first 15 terms.⠀⠀⠀

Solution:-

We know that,

Sum of n terms of A.P =$\frac{n}{2}[2a \: + \: (n - 1)d]$

In which,

• n = Number of terms.
• a = First term of A.P.
• d = Common difference.

⠀⠀⠀⠀⠀⠀

➣n = Number of terms = 15 terms.

➣a = First term = 10

➣d = a₂ - a₁ (a₁ = 10 and a₂ = 6)

= 6 - ( 10)

= -4

➣Common difference = -4

⠀⠀⠀⠀⠀⠀

So, Put the a , n and d in formula,

$\implies \sf \: \frac{15}{2}[2 \times 10 + (15 - 1) \times(- 4)]$

$\implies \sf \: \frac{15}{2}[20 + (14)\times( - 4)]$

$\implies \sf \: \frac{15}{2}[20 + ( -56)$

$\implies \sf \: \frac{15}{2}\times (-36)$

• 36 get cut 18 times with the table of 2.

$\implies \sf \: 15 \times (-18)$

$\implies \sf \: -270$

⠀⠀⠀

Therefore,

❛Sum of 15 terms of A.P is -270.❜