Answer:-602
Step-by-step explanation:
First term=a=-143
common difference=d=-134-(-143)=9
Using the formula
Sn=n/2(2a+d(n-1))
S28=28/2 (2(-143)+9(28-1))
S28=14(-286+9x27)
S28=14(-286+243)
S28=14(-43)
S28=-602
