SOLUTION: Find a1 for the arithmetic sequence: a7=40,a22=-100

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Question 35843: Find a1 for the arithmetic sequence:
a7=40,a22=-100
Answer by stanbon(75887) About Me  (Show Source):
You can put this solution on YOUR website!
a(7)=a(1)+6d = 40
a(22)=a(1)+21d=-100
Subtract the 1st from the 2nd to get:
15d=-140
d=-28/3
Now solve for a(1) in the 1st:
a(1)+6(-28/3)=40
a(1)-56=40
a(1)=96
Cheers,
Stan H.