It's not at all obvious! But have a look at https://proofwiki.org/wiki/Sum_of_Sequence_of_Cubes for a proof.
You can probably do this on the web2 calc as well but i don't know how.
anyway, I got you the answer.
It's not at all obvious! But have a look at https://proofwiki.org/wiki/Sum_of_Sequence_of_Cubes for a proof.
1^3 + 2^3 + 3^3 + 4^3 + 5^3 +.... 2014^3 ?
s1=1+2+3+...+n
\begin{array}{llcl} & (1+i)^2 &=& i^2+2i+1 \\ & (1+i)^2 - 1 &=& 1+2i \\ \hline i=1 & \not{2^2}-1^2 &=& 1+ 2*1\\ i=2 & \not{3^2}-\not{2^2} &=& 1+ 2*2 \\ i=3 & \not{4^2}-\not{3^2} &=& 1+ 2*3 \\ ... &... &...& ... \\ i=n & (1+n)^2-\not{n^2} &=& 1+2n\\ \hline \Sigma & (1+n)^2-1&=&n+2*(\underbrace{1+2+3+...+n}_{s_1}) \end{array}\\ (1+n)^2-1&=&n+2s_1\\ n+n^2=2s_1\\ \boxed{s_1=\dfrac{n(n+1)}{2}}
s2=12+22+32+...+n2
(1+i)3=i3+3i2+3i+1(1+i)3−i3=1+3i2+3ii=1⧸23−13=1+3∗12+3∗1i=2⧸33−⧸23=1+3∗22+3∗2i=3⧸43−⧸33=1+3∗32+3∗3............i=n(1+n)3−⧸n3=1+3∗n2+3nΣ(1+n)3−1=n+3∗(12+22+32+...+n2⏟s2)+3∗(1+2+3+...+n⏟s1)(1+n)3−1=n+3s2+3s1(1+n)3−1=n+3s2+3∗n∗(n+1)2s2=n∗(16+n2+n23)s2=n6∗(1+3n+2n2)s2=n6(n+1)(2n+1)
s3=13+23+33+...+n3
(1+i)4=i4+4i3+6i2+4i+1(1+i)4−i4=1+4i3+6i2+4ii=1⧸24−14=1+4∗13+6∗12+4∗1i=2⧸34−⧸24=1+4∗23+6∗22+4∗2i=3⧸44−⧸34=1+4∗33+6∗32+4∗3............i=n(1+n)4−⧸n4=1+4∗n3+6∗n2+4∗nΣ(1+n)4−1=n+4∗(13+23+33+...+n3⏟s3)+6∗(12+22+32+...+n2⏟s2)+4∗(1+2+3+...+n⏟s1)(1+n)4−1=n+4s3+6s2+4s1(1+n)4−1=n+4s3+6∗n6(n+1)(2n+1)+4∗n∗(n+1)24∗s3=n4+4n3+6n2+4n−n−2n3−3n2−n−2n2−2n4∗s3=n4+2n3+n2s3=n2∗(n+1)24
13+23+33+43+53+....20143=(2014∗20152)2=20291052=4117267101025