Stuck on geometric series question (in picture)

The value of a7 is 128

Step-by-step explanation:

* Lets revise the rule of the geometric series

-There is a constant ratio between each two consecutive numbers

- Ex:

# 5  ,  10  ,  20  ,  40  ,  80  ,  ………………………. (×2)

# 5000  ,  1000  ,  200  ,  40  ,  …………………………(÷5)  

* General term (nth term) of a Geometric series:

# a1 = a  ,  a2  = ar  ,  a3  = ar2  ,  a4 = ar3  ,  a5 = ar4

# an = ar^n-1, where a is the first term , r is the constant ratio

   between each two consecutive terms , and n is the position

   of the term in the series

* Now lets solve the problem

∵ a = 2

∵ r = -2

* To find a7 put n = 7

∵ an = a (r)^n - 1

∴ a7 = 2 (-2)^(7 - 1) = 2 (-2)^6

∵ (-2)^6 = 64 ⇒ even power canceled the negative sign

∴ a7 = 2 (64) = 128

∴ The series is : 2 , -4 , 8 , -16 , 32 , -64 , 128 ,

* The value of a7 is 128

definition: a circle is the  set of all points in a plane that are equidistant  from a given  point  called the center of the circle. we use the symbol ⊙ to represent a circle. the a line segment from the center of the circle to  any point  on the circle is a radius of the circle.

step-by-step explanation:

i googled it and this is what i got i don't know how it is. sorry.

3

step-by-step explanation:

in standard form:

a= dictionaries

b= maps

you have to buy 3 dictionaries, so put a 3 next to the a (dictionaries) so that you can multiply them by each other.

a3+b= 60 (the amount of money you have)

we already know the cost of a=15 so replace a with $15

($15 x 3)+b=60

multiply 15 and 3 to get $45 and replace it with $45

45+b=60

and then replace b with 15 to get the total:

45+15=60

that means you have $15 left after buying 3 dictionaries.

15 divided by the cost of a map ($5) equals 3.

so you can buy 3 maps.

sorry if it was confusing!