第4章 4.6

(1)

$4x^2-4x+1=0$

$(2x-1)^2=0 \quad x=\dfrac{1}{2}$

(2)

$9x^2+6x+1=0$

$(3x+1)^2=0 \quad x=-\dfrac{1}{3}$

(3)

$50x^2-20x+2=0$

$(5x-1)(10x-2)=0 \quad x=\dfrac{1}{5}$

(4)

$12x^2+27-36x=0$

$3(4x^2-12x+9)=3(2x-3)^2=0 \quad x=\dfrac{3}{2}$