(2)、\(X\)的三阶中心矩为
A: \(0\)
B: \(\frac{1}{12}\)
C: \(\frac{1}{6}\)
D: \(\frac{1}{3}\)
A: \(0\)
B: \(\frac{1}{12}\)
C: \(\frac{1}{6}\)
D: \(\frac{1}{3}\)
举一反三
- 已知三阶矩阵`A`的特征值为`-1,1,2`，`A^**`表示`A`的伴随阵，则矩阵` B=(3A^**)^{-1} ` 的特征值为（ ） A: `1,-1,2`； B: `\frac{1}{6},-\frac{1}{6},-\frac{1}{3}`； C: `-\frac{1}{6},\frac{1}{6},\frac{1}{3}`； D: `\frac{1}{2},-\frac{1}{2},-1`。
- 微分方程$y' = \sqrt{x},y(1)=0$的解为 A: $ \frac{2}{3} x^{\frac{3}{2}} + C $ B: $ \frac{2}{3} x^{\frac{3}{2}} -\frac{2}{3} $ C: $ x^{\frac{3}{2}}-1 $ D: $ x^{\frac{3}{2}}+C $
- For the integral $\int_0^{+\infty}\frac{dx}{(x^2+p^2)(x^2+q^2)}$, which of the following statements are CORRECT? A: $\frac{1}{q^2-p^2}[\frac{1}{p}-\frac{1}{q}]\frac{\pi}{2},p>0 \ q>0;$ B: $\frac{1}{q^2-p^2}[\frac{1}{q}+\frac{1}{p}]\frac{\pi}{2}, -p>0 \ -q>0;$ C: $\frac{1}{q^2-p^2}[\frac{1}{p}-\frac{1}{q}]\frac{\pi}{2}, p>0 \ -q>0;$ D: $\frac{1}{p^2-q^2}[\frac{1}{q}+\frac{1}{p}]\frac{\pi}{2}, -p>0 \ q>0.$
- 将函数\(f(x)=\sin^4 x\)展开成Fourier级数为 ____ . A: \(f(x) = \frac{3}{8}-\frac{1}{2}\cos 2x +\frac{1}{8}cos 4x\) B: \(f(x) = \frac{1}{4}-\frac{1}{2}\cos x +\frac{3}{8}cos 4x\) C: \(f(x) = \frac{1}{4}-\frac{1}{2}\sin 2x -\frac{3}{8}cos 4x\) D: \(f(x) = \frac{3}{8}-\frac{1}{2}\sin x -\frac{1}{8}cos 4x\)
- \(函数f(x,y)=\ln(x+y+1)在点(0,0)处的带佩亚诺余项的三阶泰勒公式为(\,)\) A: \(x+y-\frac{1}{2}(x+y)^2+\frac{1}{6}(x+y)^3+o((\sqrt{x^2+y^2})^3)\) B: \(x+y-\frac{1}{2}(x+y)^2+\frac{1}{3}(x+y)^3+o((\sqrt{x^2+y^2})^3)\) C: \(x+y-\frac{1}{3}(x+y)^2+\frac{1}{6}(x+y)^3+o((\sqrt{x^2+y^2})^3)\) D: \(x+y-\frac{1}{2}(x+y)^2-\frac{1}{3}(x+y)^3+o((\sqrt{x^2+y^2})^3)\)