Calculus

How many terms are required in the series (-6) + (-12) + (-24)... to add to a sum of -378?

How do I do this?

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  1. looks like a geometric series where
    a = -6 and r = 2
    Term(n) = a(r^n - 1)/(r-1), where n is the number of terms
    -378 = -6(2^n - 1)/(2-1)
    63 = 2^n - 1
    64 = 2^n
    I know that 2^6 = 64
    so n=6

    so you need 6 terms.

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  2. Thank you so much, could you please help me with my other calculus posts.

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