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设f(x,y)=x3+3x2+y2-9x-2y,则有()。
A . (1,1)是极小点,(-3,1)是极大点
B . (1,1)是极大点,(3,1)是极小点
C . (1,1)是极小点,(-3,1)不是极值点
D . (1,1),(-3,1]都不是极值点
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设线性无关函数y1、y2、y3都是二阶非齐次线性方程y″+P(x)y′+Q(x)y=f(x)的解,C1、C2是待定常数。则此方程的通解是:()
A . C
y
+C
y
+y
B . C
y
+C
y
-(C
+C
)y
C . C
y
+C
y
-(1-C
-C
)y
D . C
y
+C
y
+(1-C
-C
)y
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设线性无关函数y1、y2、y3都是二阶非齐次线性方程y″+P(x)y′+Q(x)y=f(x)的解,c1、c2是待定常数。则此方程的通解是:()
A . c1y1+c2y2+y3
B . c1y1+c2y2-(c1+c3)y3
C . c1y1+c2y2-(1-c1-c2)y3
D . c1y1+c2y2+(1-c1-c2)y3
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设f(x)具有二阶导数,y=f(x2),则的值为()。
A . f"(4)
B . 16f"(4)
C . 2f'(4)+16f"(4)
D . 2f'(4)+4f"(4)
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D域由x轴,x2+y2-2x=0(y≥0)及x+y=2所围成,f(x,y)是连续函数,转化
https://assets.asklib.com/psource/2015102917113774223.jpg
为二次积分为()。
A .https://assets.asklib.com/psource/2015102917120475964.jpg
B .https://assets.asklib.com/psource/2015102917122295048.jpg
C .https://assets.asklib.com/psource/2015102917123985716.jpg
D .https://assets.asklib.com/psource/2015102917125224591.jpg
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F(x,y)=x2+y2在x+y-1=0上取得的极小值为()。
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设z=x+y+f(x-y),且当y=0时,z=x2,则函数z=______
设z=x+y+f(x-y),且当y=0时,z=x<sup>2</sup>,则函数z=______
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设f(x,y)=ecosx(2x-y),求f&39;x(0,1),f&39;y(0,1).
设f(x,y)=e<sup>cosx</sup>(2x-y),求f&39;<sub>x</sub>(0,1),f&39;<sub>y</sub>(0,1).
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设x=2<sup>1110</sup>·0.101100l1,y=2<sup>111</sup>·011100110,求f(x±y)f(x*y).
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设F(x+y+z,x2+y2+z2)=0,F对各变量具有一阶连续偏导数,求由F=0所确定的函数z=f(x,y)的梯度.
设F(x+y+z,x<sup>2</sup>+y<sup>2</sup>+z<sup>2</sup>)=0,F对各变量具有一阶连续偏导数,求由F=0所确定的函数z=f(x,y)的梯度.
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设(X,Y)的联合概率密度为其中(I)求边缘概率密度f<sub>X</sub>(x)和f<sub>Y</sub>(y);(II)(X,Y)是否为正态随机
设(X,Y)的联合概率密度为
<img src='https://img2.soutiyun.com/ask/2020-11-17/974480299608746.png' />
其中<img src='https://img2.soutiyun.com/ask/2020-11-17/974480313640548.png' />
(I)求边缘概率密度f<sub>X</sub>(x)和f<sub>Y</sub>(y);
(II)(X,Y)是否为正态随机变量?X与Y是否独立?
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设函数z=z(x,y)由方程x2+y2+z2=xf(y/x)确定,求
设函数z=z(x,y)由方程x2+y2+z2=xf(y/x)确定,求
<img src='https://img2.soutiyun.com/ask/uploadfile/9084001-9087000/2c62d325d54a3f32b199ab456ce61558.jpg' />
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已知微分方程 (x2+y)dx+f(x)dy=0 有积分因子μ=x,试求所有可能的函数f(x).
已知微分方程 (x2+y)dx+f(x)dy=0 有积分因子μ=x,试求所有可能的函数f(x).
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设f(x)在(0,+∞)内有定义,且f'(1)=a(≠0),又对,y∈(0,+∞),有f(xy)=f(x)+f(y),求f'(x).
设f(x)在(0,+∞)内有定义,且f'(1)=a(≠0),又对<img src='https://img2.soutiyun.com/ask/2021-01-13/979379872126164.png' />,y∈(0,+∞),有f(xy)=f(x)+f(y),求f'(x).
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设f"(x)存在,求下列函数的二阶导数;(1) y=f(x<sup>2</sup>);(2)y=ln[f(x)].
设f"(x)存在,求下列函数的二阶导数<img src='https://img2.soutiyun.com/ask/2020-11-10/973871310253584.png' />;
(1) y=f(x<sup>2</sup>);(2)y=ln[f(x)].
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d域由x轴,x2+y2-2x=0(y≥0)及x+y=2所围成,f(x,y)是连续函数,转化
D域由x轴,x2+y2-2x=0(y≥0)及x+y=2所围成,f(x,y)是连续函数,转化<img src='https://img2.soutiyun.com/shangxueba/ask/17667001-17670000/17667782/2015102917113774223.jpg' />为二次积分为()。
A.<img src='https://img2.soutiyun.com/shangxueba/ask/17667001-17670000/17667782/2015102917120475964.jpg' />
B.<img src='https://img2.soutiyun.com/shangxueba/ask/17667001-17670000/17667782/2015102917122295048.jpg' />
C.<img src='https://img2.soutiyun.com/shangxueba/ask/17667001-17670000/17667782/2015102917123985716.jpg' />
D.<img src='https://img2.soutiyun.com/shangxueba/ask/17667001-17670000/17667782/2015102917125224591.jpg' />
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设f(x+y,x-y)=x<sup>2</sup>-y<sup>2</sup>-xy,求f(x,y).
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设函数y1,y2,y3都是线性非齐次方程y″+p(x)y′+q(x)y=f(x)的不相等的特解,则函数y=(1-c1-c2)y1+c1y2+c2y3()。(c1,c2为任意常数)
A.是所给方程的通解
B.不是方程的解
C.是所给方程的特解
D.可能是方程的通解,但一定不是其特解
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设f:NxN→N(f(<x,y>)=x+y+1(1)说明f是否为单射,满射,双射的;(2)令A={<x,y>∣x,y∈N且f(<x,y>)=3},求A(3)令B={f(<x,y>)∣x,y{1,2,3}且x=y},求B.
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设f(x)的各阶导数存在,求y"及y"';
设f(x)的各阶导数存在,求y"及y"';
<img src='https://img2.soutiyun.com/ask/2021-01-22/98015818629391.png' />
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设f(x,y)=求
设f(x,y)=<img src='https://img2.soutiyun.com/ask/2021-01-10/979126807382406.png' />求<img src='https://img2.soutiyun.com/ask/2021-01-10/97912681530886.png' />
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设f(x,y)=x+(y-1)arcsin,求f<sub>x</sub>(x,1)及f<sub>x</sub>(0,1).
设f(x,y)=x+(y-1)arcsin<img src='https://img2.soutiyun.com/ask/2020-12-22/977517951515543.png' />,求f<sub>x</sub>(x,1)及f<sub>x</sub>(0,1).
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(1)求y=Inx+e<sup>x</sup>的反函数x=x(y)的导数;(2)设y=f(x)是x=φ(y)的反函数,且f(2)-4,f(2)=3,f'(4)=1,问φ(4)等于1/3还是1?
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设z=f(x,y)满足f(x,0)=x,f(0,y)=y<sup>2</sup>,f"<sub>xy</sub>(x,y)=x+y,求f(x,y)。