在空间直角坐标系中,下面表示平面方程的是( ).
A: \( {x^2} + {y^2} + {z^2} = 4 \)
B: \( 2x - 6y + 2z - 7 = 0 \)
C: \( 3{x^2} + 4{y^2} = 1 \)
D: \( 4{y^2} + \frac { { {z^2}}}{3} = 1 \)
A: \( {x^2} + {y^2} + {z^2} = 4 \)
B: \( 2x - 6y + 2z - 7 = 0 \)
C: \( 3{x^2} + 4{y^2} = 1 \)
D: \( 4{y^2} + \frac { { {z^2}}}{3} = 1 \)
举一反三
- 4.已知二元函数$z(x,y)$满足方程$\frac{{{\partial }^{2}}z}{\partial x\partial y}=x+y$,并且$z(x,0)=x,z(0,y)={{y}^{2}}$,则$z(x,y)=$( ) A: $\frac{1}{2}({{x}^{2}}y-x{{y}^{2}})+{{y}^{2}}+x$ B: $\frac{1}{2}({{x}^{2}}{{y}^{2}}+xy)+{{y}^{2}}+x$ C: ${{x}^{2}}{{y}^{2}}+{{y}^{2}}+x$ D: $\frac{1}{2}({{x}^{2}}y+x{{y}^{2}})+{{y}^{2}}+x$
- 9. 已知函数$z=z(x,y)$由${{z}^{3}}-3xyz={{a}^{3}}$确定,则$\frac{{{\partial }^{2}}z}{\partial x\partial y}=$( ) A: $\frac{z({{z}^{4}}-2xy{{z}^{2}}-{{x}^{2}}{{y}^{2}})}{{{({{z}^{2}}-xy)}^{3}}}$ B: $\frac{z({{z}^{4}}-2xy{{z}^{2}}-xy)}{{{({{z}^{2}}-xy)}^{2}}}$ C: $\frac{z({{z}^{3}}-2xyz-{{x}^{2}}{{y}^{2}})}{{{({{z}^{2}}-xy)}^{3}}}$ D: $\frac{z({{z}^{3}}-2xy{{z}^{2}}-{{x}^{2}}y)}{{{({{z}^{2}}-xy)}^{3}}}$
- 以下方程在空间中表示柱面的是( )。 A: \( {x^2} + {y^2} + {z^2} = 1 \) B: \( z = \sqrt { { x^2} + {y^2}} \) C: \( {x^2} + {y^2} = 4 \) D: \( z = {x^2} + {y^2} \)
- 已有定义语句:int x=2,y=4,z=6;if(x>y) z=x;x=y;y=z;执行上述语句后x,y,z的值是____。 A: x=4,y=2,z=2 B: x=4,y=4,z=2 C: x=4,y=6,z=6 D: x=4,y=2,z=6
- 已知int x=1,y=2,z=3;执行if(x>y) z=x;x=y;y=z;后x,y,z的值为( ) A: x=1,y=2,z=3 B: x=2,y=3,z=3 C: x=2,y=3,z=1 D: x=2,y=3,z=2