1、x^2=1/36,x=+-1/6
2、x^2=81/4.x=+-9/2
3、x+5=+-5,x=0,或x=-10
4、(x+1)=+-2,x=1或x=-3
5、(x-3)=+-根号2,x=3+根号2或x=3-根号2