IMPORTANT FORMULAE
CHAPTER II                     NUMBER THEORY
Sl.No	Arithmatic Progression	Geometric Progression
	General Form.
1	a,a+d,a+2d,a+3d,… Here  a=t1 = First Term  d=t2 - t1= Common Difference	a,ar,ar2,ar3,… Here  a=t1= First Term   r= =common ratio
	nth  term
2	tn = a + (n-1)d	tn=arn-1
	Number of terms
3	n =   (l-a)/d + 1	__
	Sum to  'n'  terms
4	sn = n/2 [2a+(n-1)]d	sn =a[(r^n -1)/(r -1)]
	sn =n/2 [a+l]	sn =a[(〖1-r〗^n )/(1-r )]
		sn = an
	Sum to  '∞'  terms
5			S  = a/(1-r)
	Three consecutive terms
6	a -d, a, a+d		a/r, a, ar