Find a formula for the arithmetic sequence an given that a5=54 and a10=89.
An, the arithmetic sequence always has the form an=a1+d(n-1) where d is the common difference and a1 is the first term.
Plug in the information given to us in the problem to form a system of equations
Subtract the two equations to obtain
By back substituting d=7 into either of the two equations, we can find a1