先化解再求值.
先开最里面的括号,依次下去
1:(200-10(2x-20))(x-8)=640
2:(200-20x+200)(x-8)=640
3:(200-20x+200)(x-8)=640
4:(-20x+400)(x-8)=640
5:(-20x+400)(x-8)=640
6:x^2-28x+192=0
7:(x-14)^2=4
8:x1=+2+14=16 x2=-2+14=12
讲得太细了`晕~