Formula

Question 1

Nth term of an arithmetic sequence?

Answer 1

Nth term = a + d(n-1)

Question 2

Nth term of a geometric sequence

Answer 2

Nth term = ar^(n-1)

Question 3

Sum of a arithmetic sequence up to n

Answer 3

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

Or n/2 (a1 + an)

Question 4

Sum of a geometric sequence up to n

Answer 4

Sn = a(r^n -1)/r-1

Or

Sn = a(1-r^n)/1-r

Question 5

Sum to infinity of a geometric series

Answer 5

S~ = a/1-r

Question 6

Formula for a circle centre origin

Answer 6

X^2 + y^2 = r^2