the sum of first 7 term of an ap is 63 and sum of next 7 terms is 161 find 28 term of an ap
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Answer:
546
Step-by-step explanation:
A7=63
a+6d=63 ------(1)
A14=A7+161
=63+161
=224
A14=224
a+13d=224 ---------(2)
Subtracting (1) from (2), we get,
d=23
So substituting d=23 in (1),
a+6*23=63
a+138=63
a=63-138
a= -75
So, therefore d=23 and a= -75
A28=?
=a+(n-1)d
= -75+(28-1)23
= -75+27*23
= -75+621
=546
So, therefore A28 is 546.
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