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