X^4+3X^3+6X^2-4=X^4+3X^3+2X^2+4x²-4=x²(x²+3x+2)+4(x²-1)=x²(x+2)(x+1)+4(x+1)(x-1)=(x+1)(x³+2x²+4x-4)
(7X-4)(16-3X)=0 X1=7/4 X2=16/3 （3x 2）（x-4）=0 X1=-3/2 X2=4 9（2x 3）^2-4（2x-5）^2=0 (6X 9)^2-(4X-10)^2=
