Determine the ap whose fifth term is 19 and difference of eight term from thirteen term is 20
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Answered by
1
Answer:
Fifth term is 19
a+(5-1)d=19
a+4d=19.............(i)
13th term-8th term is 20
a+(13-1)d - (a+(8-1)d) = 20
a+12d-a-7d=20
5d=20
d=4
Putting d=4 in equation (i)
a+4*4=19
a=19-16
a=3
A.P. is a,a+d,a+2d..........
3,3+4,3+2*4.......
3,7,11...........
Answered by
1
Answer:
=>3,7,11,15,
Step-by-step explanation:
a5 = a a+ (5-1)d = 19 and [a+(13-1)d] - [a+(8-1)d] = 20 [∵an = a+(n-1)d]
⇒ a + 4d = 19
and a + 12d - a - 7d = 20 ⇒ 5d = 20
∴ d = 4
On putting d = 4 in Eq.(i), we get
a + 4(4) = 19
a + 16 = 19
a = 19 - 16 = 3
So, required AP is a,a+d,a+2d,a+3d,...i.e,,3,3 + 4,3 + 2(4),3 + 3(4),..
i.e.,3,7,11,15,
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