4-(x+2)(x+ 1)= 1-x^2
4-x^2-3x-2= 1-x^2
1=3x
x= 1/3
2) x ≠ 2 first, and then divide and deform.
(x-2)^2-3=x^2-4
x^2-4x+4-3=x^2-4
5 = 4 times
x=5/4
3) x≦-3 first, and then both sides of the equation are multiplied by (x+3) at the same time.
x^2-9+6x-x^2=0
6x=9
x=3/2