Is 571 a term in the A.P. series: 27, 33, 39, 45?

Here a = 27, d= 33-27 = 6

 

Let an = 571

So 571 = a + (n-1) d=  27  + (n-1) x 6

i.e 571 - 27 = 544 = (n-1) x 6

 544/ 6 = (n-1)

i.e 90.66 = n-1

n-1 is not a natuaral number  o n is not a natural number .

So 571 can not be a term of the given AP