help me solve this please :)
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sorry I did not know
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1.5th term +9th term=30
a+4d+a+8d=30
2a+12d=30
a+6d=15
a=15-6d-------(1)
25th term=3(8th term)
a+24d=3(a+7d)
a+24d=3a+21d
3d=2a
3d=2(15-6d). (using 1)
3d=30-12d
15d=30
d=2
a=15-6(2)=3
AP=3,5,7,9,11..........
2.Let the AP be (a-d),a and (a+d)
a-d+a+a+d=27
3a=27
a=9
a(a-d)(a+d)=648
9(a^2-d^2)=648
81-d^2=72
9=d^2
d=3
Required number=6,9,12
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