What is the sum of the first 7 terms of the series −8+16−32+64−
2 answers:
Lets Get started :)
The terms given are
- 8 , + 16 , - 32 , + 64
The formula for finding the sum of this geometric sequence is:
Sn =
a₁ = first term of sequence = -8
r = common ration = -2
n = term of sum we need to find = 7
Sn =
= -344
There is also another way, by simply adding, but you cannot perform this when they ask for a larger terms sums
Each term are multiplied by - 2, so to find the rest of the terms, we multiply by - 2
+ 64 x - 2 = - 128
- 128 x -2 = + 256
+256 x - 2 = - 512
( - 8 ) + ( 16 ) + ( - 32 ) + ( 64 ) + ( - 128 ) + ( 256 ) + ( - 512 ) (first 7 terms)
= -344
The terms given are
- 8 , + 16 , - 32 , + 64
The formula for finding the sum of this geometric sequence is:
Sn =
a₁ = first term of sequence = -8
r = common ration = -2
n = term of sum we need to find = 7
Sn =
= -344
There is also another way, by simply adding, but you cannot perform this when they ask for a larger terms sums
Each term are multiplied by - 2, so to find the rest of the terms, we multiply by - 2
+ 64 x - 2 = - 128
- 128 x -2 = + 256
+256 x - 2 = - 512
( - 8 ) + ( 16 ) + ( - 32 ) + ( 64 ) + ( - 128 ) + ( 256 ) + ( - 512 ) (first 7 terms)
= -344
You might be interested in
The given displacement at time, t, is
p(t) = 2 sin(t³) + 5 cos(t³)
The initial equilibrium position is
p(0) = 5
To determine future equilibrium postions, define
f(t) = p(t) - 5 = 2 sin(t³) + 5 cos(t³ - 5
The derivative of f(t) is
f'(t) = (3t²)[2 cos(t³) - 5sin(t³)]
Equilibrium is established when f(t) = 0.
To solve this equation numerically, we shall use the Newton-Raphson method, given by.
t(n+1) = t(n) - f[t(n)]/f'[(t(n)], n=0,1,2, ...,
As a guess, let (0) = 1.
The iterative solution for t is shown below.
n t(n)
--- -----------
0 1.0000
1 0.9344
2 0.9147
3 0.9130
4 0.9130
The solution converges rapidly to t = 0.913 s.
The graphical solution (shown below) confirms the numerical solution.
Answer:
The weight first reaches the equilibrium position in 0.913 sec.
p(t) = 2 sin(t³) + 5 cos(t³)
The initial equilibrium position is
p(0) = 5
To determine future equilibrium postions, define
f(t) = p(t) - 5 = 2 sin(t³) + 5 cos(t³ - 5
The derivative of f(t) is
f'(t) = (3t²)[2 cos(t³) - 5sin(t³)]
Equilibrium is established when f(t) = 0.
To solve this equation numerically, we shall use the Newton-Raphson method, given by.
t(n+1) = t(n) - f[t(n)]/f'[(t(n)], n=0,1,2, ...,
As a guess, let (0) = 1.
The iterative solution for t is shown below.
n t(n)
--- -----------
0 1.0000
1 0.9344
2 0.9147
3 0.9130
4 0.9130
The solution converges rapidly to t = 0.913 s.
The graphical solution (shown below) confirms the numerical solution.
Answer:
The weight first reaches the equilibrium position in 0.913 sec.