4.(x+1)(x+2)=(2x-1)(x+1)
x+2/3-x²-3/2=2
→x²-x+17/6=0
∴x=无解
2.(x+5)²-2(x+5)-8=0
→﹙x+5+2﹚﹙x+5-4﹚=0
∴x1=-7; x2=-1
3.(x+3)(x-1)=5
→x²+2x-8=0
∴﹙x-2﹚﹙x+4﹚=0
∴x1=-4; x2=2
→(x+1)(x -3﹚=0
∴ x=3
或 x=-1