1、x^2十4x一5=0
解:(x一2)^2=3^2
x一2=土3
x1=5,x2=一1
(2)x^2一3x十2=0
解:(x一2)(x一1)=0
x1=2,x2=1
(3)x^2十6x一10=0
解:(x十3)^2=19
x十3=土√19
x1=一3十√19
x2=一3一√19
(4)x^2一3x一7/4=0
解:(x一3/2)^2=13/4
x一3/2=土√13/2
x1=(3十√13)/2
x2=(3一√13)/2
(5)2x^2十4x一6=0
解:x^2十2x一3=0
(x十3)(x一1)=0
x1=一3,x2=1