Write the sum using summation notation, assuming the suggested pattern continues.

3 - 15 + 75 - 375 + ...

Question

Write the sum using summation notation, assuming the suggested pattern continues.

3 - 15 + 75 - 375 + ...

anonymous · Answer

geez,  no one ever posts an easy one  ?

anonymous · Answer

@Luis_Rivera @helpmepleas239843 it has to be in summation notation form

anonymous · Answer

sorry that was incorrect one moment

anonymous · Answer

@helpmeplease239843  has this one

anonymous · Answer

$$\Sigma $$ on the bottom would be 1 on the top would be the infinite symbol on the right.....

anonymous · Answer

@helpmeplease239843 on the answer choices, each one say on the bottom is n=0

anonymous · Answer

oh on the right would be $$3(-5)^{n-1} $$ I think is that an option

anonymous · Answer

How did you get that

anonymous · Answer

the formula for the right is $$a _{n}=a _{1}r ^{n-1}$$
$$a _{1}=3$$  r=second number/first number so r=-15/3 or -5
then simply plug in the values

anonymous · Answer

I'm learning the same thing as you right now

anonymous · Answer

thanks for your help

anonymous · Answer

no problem