(1)x^2-5x+6=0 (2) x^2+x+56=0 (3)(x+8)(x+1)= -12 (4)(x+1)^2- 3(x+1)+2=0 (5)x^2-4x+4=0 (6)x^2+x-1=0

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(1)x^2-5x+6=0(2)x^2+x+56=0(3)(x+8)(x+1)=-12(4)(x+1)^2-3(x+1)+2=0(5)x^2-4x+4=0(6)x^2+x-1=0(1)x^2-5x+6

(1)x^2-5x+6=0 (2) x^2+x+56=0 (3)(x+8)(x+1)= -12 (4)(x+1)^2- 3(x+1)+2=0 (5)x^2-4x+4=0 (6)x^2+x-1=0
(1)x^2-5x+6=0 (2) x^2+x+56=0 (3)(x+8)(x+1)= -12 (4)(x+1)^2- 3(x+1)+2=0 (5)x^2-4x+4=0 (6)x^2+x-1=0

(1)x^2-5x+6=0 (2) x^2+x+56=0 (3)(x+8)(x+1)= -12 (4)(x+1)^2- 3(x+1)+2=0 (5)x^2-4x+4=0 (6)x^2+x-1=0
(1)x²-5x+6=0
(x-2)(x-3)=0
x1=2,x2=3
(2) x²+x+56=0
△=1²-4×56<0
所以此方程无实数根
(3)(x+8)(x+1)= -12
x²+9x+20=0
(x+4)(x+5)=0
x1=-4,x2=-5
(4)(x+1)²- 3(x+1)+2=0
(x+1-1)(x+1-2)=0
x1=0,x2=1
(5)x²-4x+4=0
(x-2)²=0
x1=x2=2
(6)x²+x-1=0
配方得(x+1/2)²=5/4
x+1/2=±√5/2
x1=-1/2+√5/2,x2=-1/2-√5/2