1)(X-5)(x+7)=0
X^2+7x-5x-35=0
X^2+2x-35=0
D=2^2-4×(-35)=4+140=12^2
X1=-2+12/2=10/2=5 x2=-2-12/2=-14/2=-7
2)x(x+3,2)(2x-6)=0
(X^2+3;2x)(2x-6)=0
2x^3-6x^2+6,4x^2-19,2=0
X(2x^2-6x+6,4-19,2)=0
X=0
2x^2+0,4x-19,2=0
D=0,4^2-4×2×(-19,2)=0,16+153,6=153,76=12,4^2
X1=-0,4+12;4/2×2=12/4=3 x2=-0,4-12;4/2×2=12,8/4=3,2