All categories

3 years ago

What is the sum of the geometric sequence -3,18,-108,.. if there are 7 terms?

Mathematics

1 answer:

andreev551 [17]3 years ago

5 0

Answer:

$S_{7}$ = - 119973

Step-by-step explanation:

The sum to n terms of a geometric sequence is

$S_{n}$ = $\frac{a(r^n-1)}{r-1}$

where a is the first term and r the common ratio

Here a = - 3 and r = 18 ÷ - 3 = - 6 , thus

$S_{7}$ = $\frac{-3(-279936-1)}{-6-1}$

= $\frac{-3(-279937)}{-7}$

= $\frac{839811}{-7}$

= - 119973

You might be interested in

Which is an equation of a circle with center (2, -10) and radius 3?

Ilya [14]

C.(x-2)^2+(y+10)^2=9, plug the numbers in the original formula.

6 0

3 years ago

The pool at the apartment building is 30 feet long, 20 feet wide, and 5 feet deep. It has been filled 4 feet deep. How many more

egoroff_w [7]

I think the answer is A 600 cubic feet

6 0

3 years ago

The value of a dirt bike decreases by 20% each year. If you purchased this dirt bike today for $500, to the nearest dollar how m

jeka94

The value of the bike after a year becomes only 80% of the value a year ago. In this given, the initial amount $500 should be multiplied by 80% 5 times. The answer would be $163.84. Thus, after 5 years the dirt bike would only be $163.84.

5 0

4 years ago

Read 2 more answers

Solve the equation 12+ 0.35×=20.05

lbvjy [14]

12 + 0.35X = 20.05
12 + 0.35X - 12 = 20.05 - 12
0.35X = 8.05
0.35X/0.35 = 8.05/0.35
X = 23
Hope this helps!!

8 0

3 years ago

Just Need A Few Questions Answered To Finish My Quiz, Any Help Would Be Much Appreciated.

kvv77 [185]

Given the triangle

PQR

with points

P(8,0)

Q(6,2)

R(-2,-4)

And the triangle

P'Q'R'

with points

P'(4,0)

Q'(3,1)

R'(-1,-2)

Part A. Scale factor

Using the vertex

P( 8, 0)

P'(4,0)

the dilatation factor is given by

$\frac{4}{8}=\frac{1}{2}$

The triangle has a dilatation factor of 1/2

Part B:

P''Q''R'' after using P'Q'R' reflected about the y axis

to make a reflection over the y axis

coordinates (x,y) turn into coordinates (-x,y)

as follows

$P^{\prime}(4,0)\rightarrow P^{\prime\prime}(-4,0)$ $Q^{\prime}(3,1)\rightarrow Q^{\prime\prime}(-3,1)$ $R^{\prime}(-1,-2)\rightarrow R^{\prime\prime}(1,-2)$

Then triangle P''Q''R'' has coordinates

P''(-4,0)

Q''(-3,1)

R''(1,-2)

Part C:

PQR is congruent to P''Q''R''?

Congruent triangles are triangles that have the same size and shape. This means that the corresponding sides are equal and the corresponding angles are equal.

Then the triangles are not congruent

8 0

1 year ago