Question

plz plz plz help me out!!!
I need step by step explanation ​

Answer 1

Answer:-142

Step-by-step explanation:

Sum of terms in an AP = $S_{n} =n/2(a+a_n)$

$Here, a=3,\\d=0-3=-3\\a_n=a+(n-1)d=-27\\3+(n-1)-3=-27\\-3(n-1)=-30\\3(n-1)=30\\n-1=10\\n=11$

$S_n=n/2(a+a_n)\\=11/2(3+(-27))\\=11/2*(-24)\\=11*-12\\=-142$