Question

find the sum of the arithmetic progression: -26,-24,-22....to 36 terms

Answer 1

here
a=-26,

d=(-24)-(-26),

d=-24+26=2,

n=36,

then

Sum=36/2 [2×(-26)+(36-1)×2],

Sum=18[-52+35×2],

Sum=18[-52+70],

Sum=18×18,

Sum=324