Lauran29
Answered

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write a rule for the nth term of the arithmetic sequence a8=-15 a17=-78

Sagot :

ayden9574

Answer:

Find the 40th term for the arithmetic sequence in which

a8=60 and a12=48 .

Substitute 60 for a8 and 48 for a12 in the formula

an=a1+(n−1)d  to obtain a system of linear equations in terms of a1 and d .

a8=a1+(8−1)d→60=a1+7da12=a1+(12−1)d→48=a1+11d

Subtract the second equation from the first equation and solve for d .

12=−4d−3=d

Then 60=a1+7(−3) .  Solve for a .

60=a1−2181=a1

Now use the formula to find a40 .

a40=81+39(−3)=81−117=−36 .  

Step-by-step explanation:

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