(1)5X²-1=4X
5X²-1-4X=0
(5x+1)(x-1)=0
x1=-1/5,x2=1
(2)4X²=81
2x=±9
x1=9/2,x2=-9/2
(3)4X(X+2)=25
4x²+8x-25=0
x={-8±√【(8²-4*4*(-25)】}/(2*4)
x1=(-1+√29)/2,x2=(-1-√29)/2
(4)(3X-2)(X+1)=8X-3
3x²+x-2-8x+3=0
3x²-7x+1=0
x={7±√[(-7)²-4*3*1]}/(2*3)
x1=(7+√37)/6,x2=(7-√37)/6