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Can someone help me write this into a series?

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Pablo Garcia
Pablo Garcia 2018-11-3
评论： Zackary Fillbrandt 2020-5-9
S=2*r^3 + 4*r^5 + 6*r^7+ 8*r^9 + ... + (2n)*r^(2n+1)

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回答（3 个）

Stephen23
Stephen23 2018-11-3
编辑：Stephen23 2018-11-3
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))
  5 个评论
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Stephen23
Stephen23 2020-5-8
I don't see why you need any loop:
>> n = 5;
>> (n*(n+1))/2
ans = 15
Zackary Fillbrandt
Zackary Fillbrandt 2020-5-9
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

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KALYAN ACHARJYA
KALYAN ACHARJYA 2018-11-3
编辑：KALYAN ACHARJYA 2018-11-3
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);
  1 个评论
Zackary Fillbrandt
Zackary Fillbrandt 2020-5-8
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

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madhan ravi
madhan ravi 2018-11-3
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)
  2 个评论
madhan ravi
madhan ravi 2018-11-3
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
Zackary Fillbrandt 2020-5-8
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

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