Can someone help me write this into a series?

S=2*r^3 + 4*r^5 + 6*r^7+ 8*r^9 + ... + (2n)*r^(2n+1)

Answer 1

[Stephen23]

r = pi;
n = 4;
S = sum((2:2:2*n).*r.^(3:2:2*n+1))

Or

r = pi;
n = 4;
v = 2:2:2*n;
sum(v.*r.^(v+1))

[Zackary Fillbrandt]

Im having problems with an assiengment i was given for a Into to BME course:

i have to add this equation "(n(n+1))/2" into matlab without a while loop. so that my saved file "mysum2(n)" represents;

>> mysum2(5)

ans =

15

[Stephen23]

@Zackary Fillbrandt: what have you tried so far?

[Zackary Fillbrandt]

funtion total = mysum2 (n)

total=0;

n=1;

while n ~= -1

total = ((n) * (n+1)) / 2

end

end

I knew my set up was wrong befor i entered it into the command window, but i was trying to use the 1 exursice as a starting point, but i knew it couldnt be that easy. the other function was as follows:

function total = mysum(n)

total = 0;

i = 1;

while i <= n

total = total + i;

i = i + 1;

end

end

[Stephen23]

I don't see why you need any loop:

>> n = 5;
>> (n*(n+1))/2
ans =  15

[Zackary Fillbrandt]

thank you Steven, I'm not sure if what i did to acamplish my is what you ment, but just you saying that clicked on the light buld and i was able to salve the exercise. this is what i put:

function total = mysum2 (n)

total = 0

i = 1;

while i <= n

i = (n + 1);

total = n * i;

totalt = total / 2;

end

end

whith this i was able to create my 'mysum2.m' function and complete the exercise. so that you so much Steven

Answer 2

[KALYAN ACHARJYA]

syms r 
n=input('Enter the n number ');
s=0;
for n=1:n;
     s=2*n*r^(2*n+1)+s;
end 
disp(s);

[Zackary Fillbrandt]

Im having problems with an assiengment i was given for a Into to BME course:

i have to add this equation "(n(n+1))/2" into matlab without a while loop. so that my saved file "mysum2(n)" represents;

>> mysum2(5)

ans =

15

Answer 3

[madhan ravi]

You can tell whether the series diverges or converges by the below

syms r n
SERIES=symsum((2*n)*r^(2*n+1),n,1,inf);
fplot(SERIES)

[madhan ravi]

Or you can try the following if you want to see numbers as the sum:

syms r 
rvalue = input('r value ? ')
n1 = input('nth term ? ')
n=1:n1;
SERIES=sum((2.*n).*r.^(2.*n+1))    %to see series in symbolic form like your question
SERIES=vpa(subs(SERIES,r,rvalue),3)  %to see number with three decimal places

[Zackary Fillbrandt]

Im having problems with an assiengment i was given for a Into to BME course:

i have to add this equation "(n(n+1))/2" into matlab without a while loop. so that my saved file "mysum2(n)" represents;

>> mysum2(5)

ans =

15