數學!!!解方程!!!

........x² + 2x = a² +2a
..........x² - a² = 2a -2x
(x + a)(x - a) = 2(a - x)
(x + a)(x - a) = -2(x - a)
...........x + a = -2

數學D題目成日都吾好好Define d 符號:(
Anyway, a系math黎講9成9系constant,
所以可以當普通數做.
x^2+2x-a^2-2a=0
x={-2±√[2^2-4(1)(-a^2-2a)]}/2
x=[-2±√(4a^2+8a+4)]/2
x=(a-1)/2
or
x=(-a-3)/2

X^2+2X=a^2+2a

X=a