Question

Could someone help me with this, please, I’ve been struggling for the past few hours, and I need to finish this within the next hour or I’ll get a zero, please anyone, and thank you if you do know how to help me

Answer 1

-383.5

Explanation:

4+2.5+1+...-33.5

a=4

c.d. d=2.5-4=-1.5

l=-33.5

l=a+(n-1)d

-33.5=4+(n-1)(-1.5)

-33.5-4=(n-1)(-1.5)

-37.5=(n-1)(-1.5)

`n-1=(-37.5)/(-1.5)=25\\n=25+1=26\\n=26\\S_(26)=(n)/(2) (a+l)\\=(26)/(2) (4-33.5)\\=13(-29.5)\\=-383.5`