(20-x)(32-x)=540
640-52x+x²=540
x²-52x+100=0
(x-2）（x-50）=0
x=2或x=50 (20-x)(32-x)=540
640-52x+x²=540
x²-52x+100=0
(x-2）（x-50）=0
x=2或x=50