x(x + 3) + a(a - 3)=2(ax - 1)
⇔x(x + 3) + a(a - 3) - 2(ax - 1)=0
⇔ x^2 + 3x + a^2 − 3a − 2ax + 2 = 0
⇔(x - a)^2 + 3(x − a) + 2=0
⇔ ( x − a )^2 + 2.3/2( x − a ) + 9/4 − 1/4 = 0
⇔ ( x − a + 3/2 )^2 − 1/4 = 0
⇔ ( x − a + 3/2 + 1/2 ) ( x − a + 3/2 − 1/2 ) = 0
⇔ ( x - a + 2 ) ( x - a + 1 ) = 0
⇔ x - a + 2 = 0 hoặc x - a +1 = 0