Help me with 11 and 12 please

For every integer k from 1 to 10, inclusive the "k"th term of a certain sequence is given by (−1)(k+1)∗(12k). If T is the sum of

Katena32 [7]

Answer:

Option D. is the correct option.

Step-by-step explanation:

In this question expression that represents the kth term of a certain sequence is not written properly.

The expression is $(-1)^{k+1}(\frac{1}{2^{k}})$ .

We have to find the sum of first 10 terms of the infinite sequence represented by the expression given as $(-1)^{k+1}(\frac{1}{2^{k}})$ .

where k is from 1 to 10.

By the given expression sequence will be $\frac{1}{2},\frac{(-1)}{4},\frac{1}{8}.......$

In this sequence first term "a" = $\frac{1}{2}$

and common ratio in each successive term to the previous term is 'r' = $\frac{\frac{(-1)}{4}}{\frac{1}{2} }$

r = $-\frac{1}{2}$

Since the sequence is infinite and the formula to calculate the sum is represented by

$S=\frac{a}{1-r}$ [Here r is less than 1]

$S=\frac{\frac{1}{2} }{1+\frac{1}{2}}$

$S=\frac{\frac{1}{2}}{\frac{3}{2} }$

S = $\frac{1}{3}$

Now we are sure that the sum of infinite terms is $\frac{1}{3}$ .

Therefore, sum of 10 terms will not exceed $\frac{1}{3}$

Now sum of first two terms = $\frac{1}{2}-\frac{1}{4}=\frac{1}{4}$

Now we are sure that sum of first 10 terms lie between $\frac{1}{4}$ and $\frac{1}{3}$

Since $\frac{1}{2}>\frac{1}{3}$

Therefore, Sum of first 10 terms will lie between $\frac{1}{4}$ and $\frac{1}{2}$ .

Option D will be the answer.

3 0

3 years ago

It's a PEMDAS question

monitta

[3 * (2 + 4)] - 4

Solve inside the brackets first.
Solve the parentheses inside the brackets, (2 + 4).

[3 * (6)] - 4

Now solve 3 * 6.

18 - 4

18 - 4 = 14, so your answer is:

4 0

3 years ago

Read 2 more answers

Smallest number that can be made from 5 7 9 4

Vinil7 [7]

Answer:

Step-by-step explanation:

you want your largest digits to be in the units , tens, hundred, and then thousands

4,579

5 0

2 years ago

NEED HELP EMERGENCY ‼️

cestrela7 [59]

Answer:

A. Reflect across the y-axis

Step-by-step explanation:

if the negative sign was outside the radical then it would've been a reflection on the x-axis.

6 0

3 years ago

Read 2 more answers

A robot moving forward at a constant speed takes 2.5 hours to travel 1 kilometer. Moving forward at this same constant speed, it

makvit [3.9K]

Answer:

The length of the hallway is 10 m.

Step-by-step explanation:

Given:

Time taken to cover 1 km = 2.5 hours

Distance covered in 2.5 hours = 1 km

Therefore, speed of robot = $\frac{\textrm{Distance}}{\textrm{TIme}}=\frac{1}{2.5}=0.4\ km/h$

Now, speed is constant.

Now, time taken to cover the length of hallway = 90 s

Speed of the robot = 0.4 km/h

Converting 0.4 km/h to m/s, we multiply by the factor $\frac{5}{18}$ . This gives,

$0.4\times \frac{5}{18}=\frac{1}{9}\ m/s$

Now, distance of the hallway is equal to the product of speed and time. So,

Distance of hallway = Speed $\times$ Time

Distance of hallway = $\frac{1}{9}\times 90=\frac{90}{9}=10\ m$

Therefore, the length of the hallway is 10 m.

5 0

3 years ago