• 2022-11-02 问题

    用乙酰乙酸乙酯合成酮类,需要的条件是( )。 A: (1)5%NaOH/(2)H+ B: (1)5%NaOH/(2)H+,加热 C: (1)40%NaOH/(2)H+ D: (1)40%NaOH

    用乙酰乙酸乙酯合成酮类,需要的条件是( )。 A: (1)5%NaOH/(2)H+ B: (1)5%NaOH/(2)H+,加热 C: (1)40%NaOH/(2)H+ D: (1)40%NaOH

  • 2022-06-09 问题

    设\(z = \int_ { { x^2}}^y { { e^t}\sin t} dt\),则\({z_{xx}=}\) A: \(2{e^ { { x^2}}}\left[ {\left( {1 + 2{x^2}} \right)\sin {x^2} + 2{x^2}\cos {x^2}} \right]\) B: \( - 2{e^ { { x^2}}}\left[ {\left( {1 + 2{x^2}} \right)\sin {x^2} - 2{x^2}\cos {x^2}} \right]\) C: \( - 2{e^ { { x^2}}}\left[ {\left( {1 + 2{x^2}} \right)\sin {x^2} + 2{x^2}\cos {x^2}} \right]\) D: \( - 2{e^ { { x^2}}}\left[ {\left( {1 + 2{x^2}} \right)\cos {x^2} + 2{x^2}\sin {x^2}} \right]\)

    设\(z = \int_ { { x^2}}^y { { e^t}\sin t} dt\),则\({z_{xx}=}\) A: \(2{e^ { { x^2}}}\left[ {\left( {1 + 2{x^2}} \right)\sin {x^2} + 2{x^2}\cos {x^2}} \right]\) B: \( - 2{e^ { { x^2}}}\left[ {\left( {1 + 2{x^2}} \right)\sin {x^2} - 2{x^2}\cos {x^2}} \right]\) C: \( - 2{e^ { { x^2}}}\left[ {\left( {1 + 2{x^2}} \right)\sin {x^2} + 2{x^2}\cos {x^2}} \right]\) D: \( - 2{e^ { { x^2}}}\left[ {\left( {1 + 2{x^2}} \right)\cos {x^2} + 2{x^2}\sin {x^2}} \right]\)

  • 2022-07-24 问题

    Be(OH)2为两性氢氧化物,溶于NaOH溶液,而Mg(OH)2为碱性氢氧化物,不溶于NaOH溶液。(<br/>)

    Be(OH)2为两性氢氧化物,溶于NaOH溶液,而Mg(OH)2为碱性氢氧化物,不溶于NaOH溶液。(<br/>)

  • 2022-05-31 问题

    数学式 A: (e^(2*x)*Log(x)+x^2)/Sqr(Abs(Sinx^2-Cos2x)) B: (Exp(2*x)*Log(x)+x^2)/Sqr(Abs(Sin(x^2)-Cos(x)^2)) C: (Exp(2*x)*Ln(x)+x^2)/Sqr(Abs(Sin(x^2)-Cos(x)^2)) D: (e^(2*x)*Log(x)+x^2)/Sqr(Abs(Sin(x)^2-Cos(x)^2))

    数学式 A: (e^(2*x)*Log(x)+x^2)/Sqr(Abs(Sinx^2-Cos2x)) B: (Exp(2*x)*Log(x)+x^2)/Sqr(Abs(Sin(x^2)-Cos(x)^2)) C: (Exp(2*x)*Ln(x)+x^2)/Sqr(Abs(Sin(x^2)-Cos(x)^2)) D: (e^(2*x)*Log(x)+x^2)/Sqr(Abs(Sin(x)^2-Cos(x)^2))

  • 2022-06-19 问题

    与数学关系式[img=114x22]1803bce8722f322.png[/img]等价的C语言关系表达式是? A: x < -2 && x > 2 B: x < -2 || x > 2 C: -2 < x < 2 D: !(-2 <= x <=2) E: !(-2 <=x && x <= 2) F: x < -2, x > 2

    与数学关系式[img=114x22]1803bce8722f322.png[/img]等价的C语言关系表达式是? A: x < -2 && x > 2 B: x < -2 || x > 2 C: -2 < x < 2 D: !(-2 <= x <=2) E: !(-2 <=x && x <= 2) F: x < -2, x > 2

  • 2022-06-01 问题

    求微分方程[img=101x35]17da5f15503f795.png[/img] 的通解,实验命令为(). A: dsolve(Dy+2*x*y=x*exp(-x^2))ans=C1*exp(-x^2) + (x^2*exp(-x^2))/2 B: dsolve('Dy+2*x*y=x*exp(-x^2)','x')ans=C1*exp(-x^2) + (x^2*exp(-x^2))/2 C: dsolve('Dy+2*x*y=x*exp(-x^2)')ans=C1*exp(-x^2) + (x^2*exp(-x^2))/2

    求微分方程[img=101x35]17da5f15503f795.png[/img] 的通解,实验命令为(). A: dsolve(Dy+2*x*y=x*exp(-x^2))ans=C1*exp(-x^2) + (x^2*exp(-x^2))/2 B: dsolve('Dy+2*x*y=x*exp(-x^2)','x')ans=C1*exp(-x^2) + (x^2*exp(-x^2))/2 C: dsolve('Dy+2*x*y=x*exp(-x^2)')ans=C1*exp(-x^2) + (x^2*exp(-x^2))/2

  • 2022-06-07 问题

    求不定积分[img=132x48]17da6537fc8dad6.png[/img]; ( ) A: -(4*(cos(x/2)/2 + 2*sin(x/2)))/(17*exp(2*x)) B: (4*(sin(x/2)/2 + 2*sin(x/2)))/(17*exp(2*x)) C: (4*(cos(x/2)/2 + 2*sin(x/2)))/(17*exp(2*x)) D: (4*(cos(x/2)/2 + 2*cos(x/2)))/(17*exp(2*x))

    求不定积分[img=132x48]17da6537fc8dad6.png[/img]; ( ) A: -(4*(cos(x/2)/2 + 2*sin(x/2)))/(17*exp(2*x)) B: (4*(sin(x/2)/2 + 2*sin(x/2)))/(17*exp(2*x)) C: (4*(cos(x/2)/2 + 2*sin(x/2)))/(17*exp(2*x)) D: (4*(cos(x/2)/2 + 2*cos(x/2)))/(17*exp(2*x))

  • 2022-06-11 问题

    求函数[img=148x49]17da6537a5eee98.png[/img]的导数; ( ) A: 1/(x^2*(2/x^2 + 1)) B: -1/(x^2*(2/x^2 + 1)) C: (x^2*(2/x^2 + 1)) D: -1/(x^2*(2/x^2 + 1))+2/x^2 + 1

    求函数[img=148x49]17da6537a5eee98.png[/img]的导数; ( ) A: 1/(x^2*(2/x^2 + 1)) B: -1/(x^2*(2/x^2 + 1)) C: (x^2*(2/x^2 + 1)) D: -1/(x^2*(2/x^2 + 1))+2/x^2 + 1

  • 2022-06-03 问题

    在x值处于-2~2、4~8时值为“真”,否则为“假”的表达式是______。 A: (2>x>-2)||(4>x>8) B: !(((x<-2)||(x>2))&&((x<=4)||(x>8))) C: (x<2)&&(x>=-2)&&(x>4)&&(x<8) D: (x>-2)&&(x>4)||(x<8)&&(x<2)

    在x值处于-2~2、4~8时值为“真”,否则为“假”的表达式是______。 A: (2>x>-2)||(4>x>8) B: !(((x<-2)||(x>2))&&((x<=4)||(x>8))) C: (x<2)&&(x>=-2)&&(x>4)&&(x<8) D: (x>-2)&&(x>4)||(x<8)&&(x<2)

  • 2022-06-18 问题

    已知\( y = f({x^2}) \),假设\( f(u) \)二阶可导,则\( y'' \)为( ). A: \( 4{x^2}f''({x^2}){\rm{ + }}2f'({x^2}) \) B: \( {x^2}f''({x^2}){\rm{ + }}2f'({x^2}) \) C: \( 4{x^2}f''({x^2}){\rm{ + }}f'({x^2}) \) D: \( {x^2}f''({x^2}){\rm{ + }}f'({x^2}) \)

    已知\( y = f({x^2}) \),假设\( f(u) \)二阶可导,则\( y'' \)为( ). A: \( 4{x^2}f''({x^2}){\rm{ + }}2f'({x^2}) \) B: \( {x^2}f''({x^2}){\rm{ + }}2f'({x^2}) \) C: \( 4{x^2}f''({x^2}){\rm{ + }}f'({x^2}) \) D: \( {x^2}f''({x^2}){\rm{ + }}f'({x^2}) \)

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