Question

find the sum of the first eight terms of the AP -1,2,5,8

Answer 1

-1+2+5+8+(8+3)+(8+3+3)+(8+3+3+3)+(8+3+3+3+3)=SOMETHING USE CALCULATORZZZ

Answer 2

sum of n terms of an AP is given by

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

where n = no. of terms, a = first term and d = common difference

Answer 3

Or you could just add all those 3's

Answer 4

yes that would give the correct answer

its ok for a small number of terms but heavy work say for 502 terms - then you use the formula!