Find the sum of: (-5) + (-8) + (-11) +…..+ (-200)
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Answer:
Step-by-step explanation:
a=-5 d=-8-(-5)=-3 An=-200
An=a + (n-1)d
-200= -5 + (n-1)-3
-195=(n-1)-3
65=n-1
66=n
a=-5 d=-3 n=66
Sn= n/2 [2a + (n-1)d]
Sn=66/2 [2(-5) + 65(-3)]
Sn=33[-10 - 195]
Sn=33[-205]
Sn=-6765
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