用適當的方法解一元二次方程(1)x2+3x+1=0(2)x2-10x+9=0(3)(2x-1)2=(3x+2)2(4)(x-1)(x+2)=2(x+2)

用適當的方法解一元二次方程(1)x2+3x+1=0(2)x2-10x+9=0(3)(2x-1)2=(3x+2)2(4)(x-1)(x+2)=2(x+2)

(1)x2+3x+1=0,這裡a=1,b=3,c=1,∵b2-4ac=9-4×1×1=5>0,∴x=−3±52,∴x1=−3+52,x2=−3−52;(2)分解因式得:(x-1)(x-9)=0,可得x-1=0或x-9=0,解得:x1=1x2=9;(3)開方得:2x-1=±(3x+2),即2x-1=3x+2或2x-1=-(3x+2),∴x1=-3,x2=-15;(4)分解因式得:(x+2)(x-1-2)=0,可得x+2=0或x-3=0,解得:x1=-2,x2=3.