求下列各式的值:3x平方+(-3/2x+1/3y平方)(2x-2/3y)其中x=-1/3,y=2/3
问题描述:
求下列各式的值:3x平方+(-3/2x+1/3y平方)(2x-2/3y)其中x=-1/3,y=2/3
答
3X^2+(-3/2X+1/3Y^2)(2X-2/3Y),
=3X^2-3X^2+xy+2/3xY^2-2/9Y^3
=xy+2/3xY^2-2/9Y^3
=-1/3*2/3-2/3*1/3*4/9-2/9*8/27
=-94/243
自己写的哈,不懂就问哦
答
3x²+(-3/2x+1/3y²)(2x-2/3y)=3x²-3x²+xy+2/3xy²-2/9y³=xy+2/3xy²-2/9y³=-1/3×2/3+2/3×(-1/3)×(2/3)²-2/9×(2/3)³=-2/9-4/27-16/81=-46/81