Question

Please answer fast. Don't write wrong anwer for points​

Answer 1

Answer:

19

Step-by-step explanation:

In this AP:

 a = first term = 18

 d = com. dif. = 16 - 18 = - 2

Let the required number of terms be n.

 ⇒ sum = (n/2)( 2a + (n-1)d )

⇒ 0 = (n/2)[ 2(18) + (n-1)(-2) )

⇒ 0 = n( 36 - 2n + 2 )

⇒ 0 = n( 38 - 2n )

⇒ n = 0  or 38 - 2n = 0

⇒ 38 = 2n

⇒ 19 = n

   Hence the required number of terms is 19.

Answer 2

hey mate here is your answer a = 18 d = -2 an = 0

an = a + ( n - 1 ) × d

0 = 18 + ( n - 1 ) × -2

0 = 18 + ( -2n + 2 )

0 = 18 + 2 -2n

0 = 20 -2n

-20 = - 2n

-20 / -2 = n

10 = n

here the symbols are - × - = + so it positive

ANSWER = 10

you can check it out

a10 = 0

a + 9d = 0

18 + 9 × -2 = 0

18 + ( - 18 ) = 0

18 - 18 = 0

0 = 0