please some one help me with this sum.
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see,
19th term is 52,
∴ a + 18d = 52 ... (i)
& 38th term is 128,
∴ a + 37d = 128 ... (ii)
⇒ subtract (i) from (i)
a + 18d = 52
a + 37d = 128
- - -
_____________
-19d = -76
d = 4
now, put value of d in (i)
a + 18d = 52
a + 18×4 = 52
a + 72 = 52
a = 52 - 72
a = -20
for sum of 1st 56 terms -
put the formula of sum of nth terms and put -
n = 56
a = -20 &
d = 4
and your answer will come...
Hope it helps you.. :-)
Please mark it as the brainliest... :-)