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Answer:
800
Step-by-step explanation:
d=2r=2·400=800
Answer:
I THINK it is A
Step-by-step explanation:
I did this question before
Answer:

Step-by-step explanation:
<u>Use identities to set the equation up as a quadratic</u>

<u>Make the substitution u=cos(x) and solve the quadratic</u>
<u />


Hence, 
Answer:
S12 for geometric series: (-7.5) + 15 + (-30) + ... would be: 10237.5
Step-by-step explanation:
Given the sequence to find the sum up-to 12 terms

As we know that
A geometric sequence has a constant ratio 'r' and is defined by


















∵ 



Thus, S12 for geometric series: (-7.5) + 15 + (-30) + ... would be: 10237.5