Answer:
Explanation:
You have to use the arithmetic sequence
f(n)=f(n-1)+d
You can plug in (40,10) and (50,20)
(10)=f(1)+39d
(20)=f(1)+19d
subtract
-10=20d divide
d=-1/2
plug into one of the equations above
(10)=f(1)+39(-1/2)
10=f(1)-39/2
59/2=f(1)
f(1)=29.5
plug into formula
f(n)=29.5-1/2(n-1)
f(n)= -1/2n +30 final equation (Plug in the table values into "n") to solve