9)
In an A.P., if 13th term exceeds gth term by 20 and 20th term is 2
less than twice its 10th. Find AP.
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Step-by-step explanation:
given that
a13=a9+20
a+12d=a+8d+20
12d-8d=20
4d=20
d=20/4=5
a20=2a10-2
a+19d=2(a+9d)-2
a+19d=2a+18d-2
19d-18d=2a-a-2
d=a-2
5=a-2
a=7
for the ap
a=7
a+d=7+5=12
a+2d=7+2×5=17
hence the ap are 7;12;17..…....
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