Question

which term of the progression 28,24,20.....is zero ​

Answer 1

Answer:

HI !

20 , 19 1/4 , 18 1/2 , 17 3/4 ......

first term = a = 20 

common difference = d = 19 1/4 - 20 = 77/4 - 20 = -3/4

First negative term would be the term after the term that is zero .

Let us find which term of the A.P is zero .

If the x th term be the zero , then (x + 1)th term is the first negative term 

an = 0

an = a + (n - 1) d

0 = 20 + ( n - 1) -3/4

-20 = (n - 1) -3/4

-20 = -3/4n + 3/4

3/4n = 3/4 + 20

3/4 n = 83/4

n = 83*4/4*3

n = 83/3

n = 27th term ( approx.)

27th term is the term which is zero.

Hence, 28th term is the first negative term