The 5th and 17th terms of an AP are 7 and 25 respectively, find the 13th term
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Answer:
a13=19
Step-by-step explanation:
a5=7
a17=25
a5=a+4d
7=a+4d (equation 1)
a17=a+16d
25=a+16d (equation 2)
equation 2 - equation 1
25-7= a+16d-(a+4d)
18=a-a+16d-4d
18=12d
d=18/12=3/2
a+4d=7
a+4×3/2=7
a+6=7
a=1
a13=a+12d
=1+12×3/2
= 1+18
=19
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