3X(X-5)=(X-5)²
3x(x-5)-(x-5)²=0
[3x-(x-5)](x-5)=0
(2x+5)(x-5)=0
x=-5/2或x=53X²-5X=4 公式法3X²-5X=4 3x²-5x-4=0x={-(-5)±√[(-5)²-4*3*(-4)]}/(2*3)x=(5±√73)/6