Answer:

-2.5

Step-by-step explanation:

a1=5/2

r=5/4 - 5/2= 2

S=a1/1-r

=5/2 / 1-2

=5/2 / -1

=5/2 ÷ -1

=5/2 × 1/-1

=-5/2 or -2.5

Sana po magets mo:))