(x-21)(350-10x)=400
都除以10,得:
(x-21)(35-x)=40
展开,得:
35x-735-x^2+21x=40
-x^2+56x-775=0
x^2-56x+775=0
(x-31)(x-25)=0
x-31=0或x-25=0
x=31或x=25
(x-21)(350-10x)=400
都除以10,得:
(x-21)(35-x)=40
展开,得:
35x-735-x^2+21x=40
-x^2+56x-775=0
x^2-56x+775=0
(x-31)(x-25)=0
x-31=0或x-25=0
x=31或x=25