find 4th sum and 6th sum
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Answer:
d= -1 & a=8
a= -2& n =4
Step-by-step explanation:
15= a+(3-1)d
15 = a+2d.........eq1
125= 5 ( 2a+9d)...eq2
on solving these eq we get
d= -1
a= 8
a10= 8+9×(-1)
a10= -1
v1 sum
an= a+(n-1)2.....eq1
sn= n/2( 2a+(n-1)d)
-14= -7(2a+(n-1)2.......eq2
on solving we get
a= -2
n =4
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