x^2-x-7/4=0
（x-1/2）^2-1/4-7/4=0
(x-1/2)^2=2
x-1/2=±√2
x=1/2±√2
4x^2-6x-3=0
x^2-3/2x-3/4=0
(x-3/4)^2-9/16-12/16=0
(x-3/4)^2=21/16
x-3/4=±√21 /4
x=3/4±√21 /4
x(x+4)=8x+12
x^2+4x=8x+12
x^2-4x=12
(x-2)^2=12+4=16
x-2=±4
x1=6 x2=-2