x²-64,=（x-8)(x+8) x²y-6xy²+9y³=y(x²-6xy+9y²)=y(x-3y)² 7x+3y=13,①4x-y=2②①+②×3得：7x+3y+12x-3y=13+619x=19∴x=1 y=2