1) (х+1/2)(х-1/2) = 5/16
x^2-1/4=5/16
x^2=9/4
x=-3,3
2) (3х+1,5) (3х-1,5) = 54
9x^2-2,25=54
9x^2=56,25
x^2=6,25
x=-2,5 ; 2,5
3) 3х^2 - 4x / 2 = 5x^2 - x / 3
x/3-4x/2=5x^2-3x^2
-10x/6=2x^2
x=-6/5
4) 2x-3x^2 / 5 - 7х^2 - х / 4 = x^2 / 2
(8x-x)/4=x^2/2+3x^2/5+7x^2
7x/4=(5x^2+6x^2+70x^2)
x=35/162