Question 202023
13^3 - 11^3 = 866
------------------
{{{(a+2)^3 - a^3 = 866}}}
{{{a^3 + 6a^2 + 12a + 8 - a^3 = 866}}}
{{{6a^2 + 12a - 858 = 0}}}
{{{a^2 + 2a - 143 = 0}}}
(a-11)*(a+13) = 0
a = 11
a = -13
-------------------
a^2+c^2-2b^2=2
11^2 + 13^2 - 2*12^2 is not 2, it's -8.