设x,y为实数,则f(x,y)=x^2+4xy+5y^2-2y+2的最小值()。A. 1B. 1/2C. 2D. 3/2E. 3
9.若实数x,y满足xy+x+y=10,x²y+xy²=24,则x²+y²=()A. 4B. 28C. 34D. 44E. 52
[单选题]设xy=2x+3y,,且x、y均为正整数,若当时,xy取得最小值,则x等于( )。A.2B.6C.4D.3
[单选题]已知实数x、y满足x2+y2=1,则(1-xy)(1xy)()。A . ['['有最小值,也有最大值1B . 有最小值,也有最大值1C . 有最小值,但无最大值D . 有最大值1,但无最小值
[单选题]实数x,y,a满足x+y=a+1和xy=a2-7a+16,则x2+y2的最大值是()。A . 34B . 33C . 32D . 31
[试题]计算:(1)(2x²y+3xy²)-(6x²y-3xy²);(2)(5mn-2m+3n)+(-7m-7mn);(3)(6a²-8a+11b³)-(11a²+2b³);(4)(2ab+3b²-5)-(3ab+3b²-8)。
[试题]若|x+2|+y-3=0,则xy的值为( )。A. -8B. -6C. 5D. 6
5【判断题】设f(x,y)=(xy)/(x^2)+y,则f(xy,(x)/(y))=(xy)/(xy^3)+1.A. 对B. 错
1.函数 (x+y,xy)=(x)^2+(y)^2-xy, 则 f(x,y)=
设(x,y)=sin xy,则(x,y)=sin xy设,则