Summations

Question 1

Summation for n

Answer 1

1/2n (n+1)

Question 2

Gotta factorise out as much as you can what to do when can’t

Answer 2

Expand everything and you probably be able to factorise some kore

Question 3

How to double check answe r

Answer 3

If it’s hence a and sub in to calculator

Question 4

Like hypothesis testing probability if you want 50 to 100m

Answer 4

Gotta do 1 to 100- 1 to 49

Question 5

How to method of difference s

Answer 5

Equate summations

Do First few and last few cancel out

Question 6

Sometimes might not be able to find , so need 3 terms, to be safe out three and see pattern

Answer 6

So say in head 3 2 1 and cancel, then do same and see what you sre left with and make ti equal to what they want

Question 7

Make sure you know formula for finding new summation in algebra

Answer 7

So like if 30 to 50 you do 1 30-1 and 1 to 50

So same for n+1 to 2n

Do 1 to n and 1 to 2n and minus

REMEMBER THE WHOLE THING YOURE SUMMATING, ITS R3!

AND then expand, using brskcets etc