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A Collection of Algebraic Identities
Index
Part 3. Quadratic Polynomial as a kth Power
Part 4. Simultaneous Polynomials Made Squares
Part 7b. Equal Sums of Like Powers
Part 14. Eleventh and Higher Powers
3) March 9) September (see Articles 1-3)
4) April 10) October (see Articles 4-6)
5) May (none) 11) November (see Article 7)
6) June 12) December (see Articles 8-11)
(Pls read first: This almost 300-page book is divided into more than 30 sections. For navigation, note that the topic with a link, and those immediately below it without a link, belong to the same section. Alternatively, one can use the Home and other buttons on the sidebar. For questions and comments, feel free to email author at tpiezas@gmail.com.)
Part 0. Introduction (Link 0)
Part 1. Assorted Identities (Link 1)
Part 2. Sums of Squares (Link 2)
I. Sums of two squares
x2+y2 = zk
x2+ny2 = zk; ax2+by2 = cz2 (Link 3)
ad-bc = ±1
x2+y2 = z2+1
x2+y2 = z2-1
x2+y2 = z2+nt2
x2+y2 = z2+tk
x2+y2 = mz2+nt2
c1(x2+ny2) = c2(z2+nt2)
mx2+ny2 = mz2+nt2
II. Sums of three squares (Link 4)
x2+y2+z2 = tk
x2+y2+z2 = u2+v2
(x2-1)(y2-1) = (z2-1)2
x2+y2+z2 = u2+v2+w2
x2+y2+z2 = (u2+v2+w2)Poly(t)
x2+y2+z2 = 3xyz
III. Sums of four or five squares (Link 5)
a2+b2+c2+d2 = ek
a2+b2+c2+d2 = e2+f2
a2+b2+c2+d2 = e2+f2+g2
a2+b2+c2+d2 = e2+f2+g2+h2
a2+b2+c2+d2+e2 = f2
IV. Some Identities of Squares (Link 5b)
Euler-Aida Ammei Identity
Brahmagupta-Fibonacci Two-Square Identity
Euler Four-Square Identity
Degen-Graves-Cayley Eight-Squares Identity
V. Arnold’s Perfect Forms
Lagrange’s Identity
Difference of Two Squares Identity
Part 3. Quadratic Polynomial as a kth Power (Link 6)
I. Univariate: ax2+bx+c = z2
II. Bivariate: ax2+bxy+cy2 = zk
x2+cy2 = zk
ax2+cy2 = zk, k odd
x2+2bxy+cy2 = zk
ax2+2bxy+cy2 = zk, k odd
III. Bivariate: ax2+bxy+cy2 = dz2
ax2+bxy+cy2 = dz2
ax2+by2+cz2+dxy+exz+fyz = 0
ax2+cy2 = dzk, k > 2
I. Two variables
{x2+axy+by2, x2+cxy+dy2}
{x2-ny2, x2+ny2}
{x2+y, x+y2}
{x2+y2-1, x2-y2-1}
{x2+y2+1, x2-y2+1}
II. Three variables
{x ± y, x ± z, y ± z}
{x2-y2, x2-z2, y2-z2}
{x2+y2, x2+z2, y2+z2}
{x2+y2+z2, x2y2+x2z2+y2z2}
{-x2+y2+z2, x2-y2+z2, x2+y2-z2}
{2x2+y2+z2, x2+2y2+z2, x2+y2+2z2}
{2x2+2y2-z2, 2x2-y2+2z2, -x2+2y2+2z2}
{x2+yz, y2+xz, z2+xy}
{x2+y2+xy, x2+z2+xy, y2+z2+xy}
{x2-xy+y2, x2-xz+z2, y2-yz+z2}
{x2+axy+y2, x2+bxz+z2, y2+cyz+z2}
III. Four variables
{a2+b2+c2, a2+b2+d2, a2+c2+d2, b2+c2+d2}
{a2b2+c2d2, a2d2+b2c2}
{a2b2+c2d2, a2c2+b2d2, a2d2+b2c2}
{1+abc, 1+abd, 1+acd, 1+bcd}
I. Complete Solution
II. Transformations
III. Polynomial Parametrizations
IV. Diophantine Equations needing Pell Equations (Link 9)
I. Sums of cubes
x3+y3 = z3
x3+y3+z3+t3 = 0
x3+y3+z3 = 1
x3+y3+z3 = 2
x3+y3+z3 = (z+m)3
p(p2+bq2) = r(r2+bs2)
(x+c1y)(x2+c2xy+c3y2)k = (z+c1t)(z2+c2zt+c3t2)k
x3+y3+z3 = at3 (Link 11)
x3+y3 = 2(z3+t3)
w3+x3+y3+z3 = nt3
x3+y3+z3 = t2
xk+yk+zk = {p2, q3}, k =2,3
xk+yk+zk = tk+uk+vk, k = 1,3
xk+yk+zk = tk+uk+vk, k = 2,3
x3+y3+z3 = 3t3-t
x3+y3+z3 = m(x+y+z)
x1k+x2k+x3k+x4k = y1k+y2k, k = 1,2,3
x1k+x2k+x3k+x4k = y1k+y2k+y3k+y4k, k = 1,2,3
ax3+by3+cz3 = N (Link 12)
ax3+by3+cz3+dxyz = 0
II. Cubic polynomials as kth powers
A. Univariate: ax3+bx2+cx+d2 = tk
ax3+bx2+cx+d2 = t2
ax3+bx2+cx+d2 = t3
B. Bivariate: ax3+bx2y+cxy2+dy3 = tk
x3+y3 = t2
ax3+by3 = t2
x3+y3 = nz2
x3+ax2y+bxy2+cy3 = t2
x3+ax2y+bxy2+cy3 = t3
I. Sums of biquadrates
a4+b4 = c4+d4
pq(p2+q2) = rs(r2+s2)
pq(p2-q2) = rs(r2-s2)
pq(p2+hq2) = rs(r2+hs2)
x4+y4 = z4+nt2
x4+y4 = z4+nt4
u4+nv4 = (p4+nq4)w2
u4+nv4 = x4+y4+nz4
u4+v4 = x4+y4+nz4
x4+y4+z4 = t4 (Link 14)
x4+y4+z4 = ntk
ak+bk+ck = dk+ek+fk, k = 2,4
12.1 a+b = nc; d+e = nf (Link 15)
12.2 a+b ≠ c; d+e ≠ f
12.3 a+b±c = n(d+e±f) (Link 16)
12.4 na+b+c = d+e+nf
12.5 na+b = e+nf
12.6 a+d = n(c+f)
12.7 (a2-f2)c2 = -(b2-e2)d2
ak+bk+ck = 2dk+ek, k = 2,4
ak+bk+ck = dk+ek+fk, k = 2,3,4
x4+y4+z4 = 2(x2y2+x2z2+y2z2)-t2 (Link 17)
v4+x4+y4+z4 = ntk
vk+xk+yk+zk = ak+bk+ck+dk, k = 2,4
2(v4+x4+y4+z4) = (v2+x2+y2+z2)2
x1k+x2k+x3k+x4k+x5k = y1k+y2k+y3k, k = 1,2,3,4
x1k+x2k+x3k+x4k+x5k = y1k+y2k+y3k+y4k+y5k, k = 1,2,3,4
x14+x24+…xn4, n > 4
II. Quartic Polynomials as kth Powers (Link 18)
ax4+by4 = cz2
ax4+bx2y2+cy4 = dz2
au4+bu2v2+cv4 = ax4+bx2y2+cy4
ax4+bx3y+cx2y2+dxy3+ey4 = z2
PART 8. Fifth Powers
I. General Conjectures and Problems (Link 19)
II. Some Theorems on Equal Sums of Like Powers
III. Fifth Powers (Link 20)
5.1 Four terms
5.2 Six terms
5.3 Seven terms (Link 21)
5.4 Eight terms (Link 22)
5.5 Ten terms
5.6 Twelve terms
PART 9. Sixth Powers (Link 23)
6.1 Four terms
6.2 Six terms
6.3 Seven terms (Link 24)
6.4 Eight terms (Link 25)
PART 10. Seventh Powers (Link 26)
7.1 Eight terms
7.2 Nine terms
7.3 Ten terms (Link 27)
PART 11. Eighth Powers (Link 28)
8.1 Eight terms
8.2 Nine terms
8.3 Ten terms
8.4 Twelve terms
8.5 Fourteen terms
8.6 Sixteen terms
8.7 Seventeen terms
“Everything has beauty, but not everyone can see it.” - Confucius
“When the land is barren, plant trees.” - Jean Giono