已知z=f(3x^2y,x 3y)其中f具有连续偏导,求
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sin^2(x-y)+sin^2(y-z)+sin^2(z-x)=[1-cos2(x-y)+1-cos2(y-z)+1-cos2(z-x)]/2=3/2-[(cos2xcos2y+sin2xsin2y
∵|2x-3y+1|+(x+3y+5)的二次方=0∴2x-3y+1=0x+3y+5=0x=-2y=-1∴(-2x*y)的二次方(-y的二次方)×6xy平方的值=4x⁴y*(-y²
x3y+2x2y2+xy3=xy(x2+2xy+y2)=xy(x+y)2,∵x+y=5,∴(x+y)2=25,x2+y2+2xy=25,∵x2+y2=13,∴xy=6,∴xy(x+y)2=6×25=1
原式=(x4-xy3)+(y4-x3y)+(3xy2-3x2y)=x(x3-y3)+y(y3-x3)+3xy(y-x)=(x3-y3)(x-y)-3xy(x-y)=(x-y)(x3-y3-3xy)=(
∵x+y=4,∴(x+y)2=16,∴x2+y2+2xy=16,而x2+y2=14,∴xy=1,∴x3y-2x2y2+xy3=xy(x2-2xy+y2)=14-2=12.
令:F(x,y,z)=x^3+2y^2+(10/3)z+λ(x+y+z-1)F'(x)=3x²+λ=0①F'(y)=4y+λ=0②F'(z)=10/3+λ=0③x+y+z=1④有①②③④解得
1、隐函数对x求导得1+az/ax+yz+xy*az/ax=0,故az/ax=-(1+yz)/(1+xy);F对x求导得aF/ax=e^x*y*z^2+e^x*y*2z*az/ax;当x=0,y=1时
已知x+y=5,xy=3,代数式x3y-2x平方y平方+xy3=xy(x²-2xy+y²)=xy(x-y)²=3×[(x+y)²-4xy]=3×(25-12)=
f(x,y,z)=x^3+2y^2+10/3z
∵|x+y+1|≥0,|xy-3|≥0|x+y+1|+|xy-3|=0,∴x+y+1=0,即x+y=-1xy=3xy3+x3y=xy(x²+y²)=yx[(x+y)²-2
x+y=4,xy=2后者平方后二式相加再加后者平方
x3y+xy3=xy(x^2+y^2)=(√3-√2)(√3+√2)((√3-√2)^2)+(√3-√2)^2)=1*(3-2√6+2+3+2√6+2)=10
(1)原式=x2-(2y-3)2=x2-4y2+12y-9;(2)原式=4x6y2•(-2xy)-8x9y3÷(2x2)=-8x7y3-4x7y3=-12x7y3.
由柯西不等式可知,[(4/5)+(9/4)+(1/3)]×[5(x-y)²+4(y-z)²+3t²]≥[2(x-y)+3(y-z)+t]²=(2x+y-3z+y
(x-y)2=x2-2xy+y2=9,当x2+y2=13时,13-2xy=9,解得xy=2.当xy=2,x2+y2=13时,x3y-8x2y2+xy3=xy(x2-8xy+y2)=2×(13-8×2)
=x²(y-z)+y²(z-x)+z²(x-z+z-y)=(y-z)(x²-z²)+(z-x)(y²-z²)=(y-z)(x-z)
∵x+y=3,∴(x+y)2=9,即x2+y2+2xy=9①,又x2+y2-3xy=4②,①-②,得5xy=5,xy=1.∴x2+y2=4+3xy=7.∴x3y+xy3=xy(x2+y2)=7.故答案
∵x-y=l,xy=2,∴x3y-2x2y2+xy3=xy(x2-2xy+y2)=xy(x-y)2=2×1=2.
2x+3y=-k+2,①3x-2y=5k+3②2*①+3*②13x=13k+13所以x=k+1代入①y=-kx-y=2k+1=5k=2