Answer:
n = 9
Step-by-step explanation:
20 + 18 + ... + 6 + 4
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a = 20 ; d = -2 ; n = ?
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4 = 20 + (n-1)(-2)
-16 = (n-1)(-2)
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n-1 = 8
n = 9
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S(9) = (9/2)(20+4)
S(9) = 4.5*24
S(9) = 108
<h3>
Answer: 5 - 4i (choice A)</h3>
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Work Shown:
x = the other number
(5+4i)*x = 41
x = 41/(5+4i)
x = 41*(5-4i)/( (5+4i)*(5-4i) ) ..... see note below
x = 41*(5-4i)/( 41 )
x = (41/41)*(5-4i)
x = 5 - 4i
As a way to check, (5+4i)*(5-4i) = 5^2+4^2 = 25+16 = 41
The rule used is (a-bi)(a+bi) = a^2 + b^2
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Note: I multiplied top and bottom by (5-4i) to get rid of the imaginary term in the denominator.
The firs term
A(1)=-6+(1-1)(6)
A(1)=-6+(0)(6)
A(1)=-6
The fourh term
A(n)=-6+(n-1)(6)
A(4)=-6+(4-1)(6)
A(4)=-6+(3)(6)
A(4)=-6+18
A(4)=12
The tenth term
A(10)=-6+(10-1)(6)
A(10)=-6+(9)(6)
A(10)=-6+54
A(10)=48
Answer:
D. -6,12,48
