1,25*1000+[1000-20(X-25)]X=27000
1000X-20X(X-25)=1000(27-25)
50X-X^2+25X=100
X^2-75X+100=0
X1=2分之75+5根号209
x2=2分之75-5根号209
2 （x-30)[600-10(x-40)]=12000
(x-30)(1000-10x)=12000
(x-30)(100-x)=1200
(x-30)(x-100)=-1200
x^2-130x+3000=-1200
x^2-130x+4200=0
(x-60)(x-70)=0
x1=60 x2=70