The sum of first 20 terms of an ap is -240 and its first term is 7 .find its 24 term
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S=-240,a=7,n=20,d=?
S=n/2(2a+(n-1)d)
-240=10(2(7)+(20-1)d)
-240/10=14+19d
-24-14=19d
-38=19d
d=-2
now,n=24
A24=a+(n-1)d
A24=7+(24-1)-2
A24=7+(23)-2
A24=7-46
A24=-39
S=n/2(2a+(n-1)d)
-240=10(2(7)+(20-1)d)
-240/10=14+19d
-24-14=19d
-38=19d
d=-2
now,n=24
A24=a+(n-1)d
A24=7+(24-1)-2
A24=7+(23)-2
A24=7-46
A24=-39
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