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What is the equation for a geometric sequence with a first term of 3 and a second term of −9? an = 3(−12)n − 1 an = 3(12)n − 1 an = 3(−3)n − 1 an = 3(3)n − 1?

User Tushortz
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an=a1r^n-1
a2=a1r
-9=3r
so r = -3

then an=3(-3)^n-1
User Zahid
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