2×2x×20+2×3x×30-4×2x×3x=20×30×1/380x+180x-24x^2=200260x-24x^2=20024x^2-260x+200=06x^2-65x+50=0△=65*65-4*6*50=4225-1200=3025x1=(65+55)/12=120/12=10x2=(65-55)/12=10/12=5/6