①已知x-y=1 求x³y-2x²y²+xy³的值 ②求x²+y²-6x+4y+20的最小值,
问题描述:
①已知x-y=1 求x³y-2x²y²+xy³的值 ②求x²+y²-6x+4y+20的最小值,
①已知x-y=1 求x³y-2x²y²+xy³的值
②求x²+y²-6x+4y+20的最小值,并求此时x y的值
答
① x³y - 2 x²y² + xy³ = xy(x² - 2xy + y²) = xy (x - y)²如果 x - y = 1 x³y - 2 x²y² + xy³ = xy(x² - 2xy + y²) = xy (1)² = xy② x...