Question

In A.P A=3 P=4 then Sn=903 what is n value​

Answer 1

Answer:

n = 21

Step-by-step explanation:

a = 3

d = 4

Sn = 903

we know

Sn = n/2 [ 2a + (n-1)d ]

903 = n/2 [ 2(3) + (n-1)4 ]

1806 = n [ 6 + 4n - 4 ]

1806 = n( 2 + 4n )

1806 = 2n + 4n²

4n² + 2n - 1806 = 0

2n² + n - 901 = 0

2n² - 42n + 43n - 901 = 0

2n ( n - 21 ) + 43 ( n - 21 )

(2n + 43)(n - 21)

n = -43/2 or 21

but 'n' cannot be in fraction

therefore n = 21

hope it helps...

#BAL