y=[4/(x^2)] +{9/[400-(x^2)]}讨论其单调性,并求出X值使y最小

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$y=[4/(x^2)] +{9/[400-(x^2)]}讨论其单调性,并求出X值使y最小$

y=[4/(x^2)] +{9/[400-(x^2)]}讨论其单调性,并求出X值使y最小
y=[4/(x^2)] +{9/[400-(x^2)]}
讨论其单调性,并求出X值使y最小

y=[4/(x^2)] +{9/[400-(x^2)]}讨论其单调性,并求出X值使y最小
柯西不等式呀~
（4/x²+9/(400-x²)）×(x²+(400-x))≥(2+3)²=25
y≥25/400=1/16
取等条件是（4/x²）/(9/(400-x²)) = (x²)/(400-x²)
x=4倍根号10

4(x-y)-3(x-y)=9 5(x-y)+2(x-y)=11 3(x+y)-2(x-y)=11 4(x+y)+3(x-y)=9 9y=3x-(x-1),4(x+y)-(2x+4)=8y 根据3（x+y)-2(x-y)=11,4(x+y)+3(x-y)=9可得出x+y= ,x-y= 已知X.x+y.y-4x+2y+5=0,求4X.X-12X Y+9Y.y的值 (x-y) (x-2y)+(x+2y) (x-3y)-2(x-3y) (x-4y)= 9(x-y)^2-12(x-y)+4=快因式分解：4+12(x+y)+9(x-y)^2=? (2X-3Y)(?)=-4X^+9Y^```` 如果x+y/2=x-y/3=3x-2y+9/4,那么x= ,y=如果x+y/2=x-y/3=3x-2y+9/4,那么x= ,y= (x-y)/4+(x+y)/5=1/4 (x+y)/9-(x-y)/3=//2(x-y)/4+(x+y)/5=1/4(x+y)/9-(x-y)/3=//2 (x-4y)(2x+y)= 解二元一次方程 {3(x+y)-4(x-y)=-9 x+y/2+x-y/6=1 接二元一次4(x+y)-3(x-y)=9;5(x-y)+2(x+y)=11 3(x+y）-2（x-y）=11 4（x+y)+3（x-y）=9 已知4x=9y求(1)x+y/y (2)y-x/2x有关比例的 4x=9y,求x+y/y;y-x/2x请给我完整过程 x+y=5 2x+3y-z=9 x-y+z=4