已知\( y = {x^2}{e^{ - x}} \)，则\( y'' \)为（ ）.
A: \( 2{e^{ - x}} - 4x{e^{ - x}} - {x^2}{e^{ - x}} \)
B: \( 2{e^{ - x}} - 4x{e^{ - x}} + {x^2}{e^{ - x}} \)
C: 0
D: \( 2{e^{ - x}} - 4x{e^{ - x}} \)
A: \( 2{e^{ - x}} - 4x{e^{ - x}} - {x^2}{e^{ - x}} \)
B: \( 2{e^{ - x}} - 4x{e^{ - x}} + {x^2}{e^{ - x}} \)
C: 0
D: \( 2{e^{ - x}} - 4x{e^{ - x}} \)
举一反三
- 已知\( y = {x^2} + 4x \)，则\( dy \)为（ ）. A: \( (2x + 4)dx \) B: \( 2xdx \) C: \( ({x^2} + 4)dx \) D: \( ({x^2} + 4x)dx \)
- 求解方程组[img=218x63]1803072f0e0e849.png[/img]接近 (2,2) 的解 A: FindRoot[{x^2+y^2==5Sqrt[x^2+y^2]-4x,y==x^2},{x,2},{y,2}] B: NSolve[{x^2+y^2==5Sqrt[x^2+y^2]-4x,y==x^2},{x,2},{y,2}] C: FindRoot[{x^2+y^2==5Sqrt[x^2+y^2]-4x,y==x^2},{x,y},{2,2}] D: FindRoots[{x^2+y^2=5Sqrt[x^2+y^2]-4x,y=x^2},{x,2},{y,2}]
- 求解方程组[img=218x63]1803072e5daced1.png[/img]接近 (2,2) 的解 A: NSolve[{x^2+y^2==5Sqrt[x^2+y^2]-4x,y==x^2},{x,2},{y,2}] B: FindRoot[{x^2+y^2==5Sqrt[x^2+y^2]-4x,y==x^2},{x,2},{y,2}] C: FindRoot[{x^2+y^2==5Sqrt[x^2+y^2]-4x,y==x^2},{x,y},{2,2}] D: FindRoots[{x^2+y^2=5Sqrt[x^2+y^2]-4x,y=x^2},{x,2},{y,2}]
- 已知函数f(x)是定义在(-∞,+∞)上的奇函数,当x∈[0,+∞)时,f(x)=x()2()-4x,则当x∈(-∞,0)时,f(x)=()(5.0分)A.()x()2()+4x()B.()x()2()-4x()C.()-x()2()+4x()D.()-x()2()-4x
- 方程${{x}^{2}}{{y}^{''}}-(x+2)(x{{y}^{'}}-y)={{x}^{4}}$的通解是( ) A: $y={{C}_{1}}x+{{C}_{2}}{{e}^{x}}-(\frac{1}{2}{{x}^{3}}+{{x}^{2}})$ B: $y={{C}_{1}}x+{{C}_{2}}{{e}^{x}}-(\frac{1}{2}{{x}^{3}}+{{x}^{4}})$ C: $y={{C}_{1}}x+{{C}_{2}}x{{e}^{x}}-(\frac{1}{2}{{x}^{3}}+{{x}^{4}})$ D: $y={{C}_{1}}x+{{C}_{2}}x{{e}^{x}}-(\frac{1}{2}{{x}^{3}}+{{x}^{2}})$