(x+1)^2 * (a^2 - 7 x + a+13) = x^4 - 5x^3 + ax^2 + 2(a+13)x + a+13
b = 2a + 19
c = a + 13
a - b + c = a - 2a - 19 + a + 13 = -6
(a - b + c)^-2 = 1/36