第5章 5.15

(1)

$y'=\frac{2}{2\sqrt{2x+1}}=\frac{1}{\sqrt{2x+1}}$

(2)

$y'=\frac{2x\sqrt{x}-(1+x^2)\dfrac{1}{2\sqrt{x}}}{\sqrt{x}^2}=\frac{\dfrac{4x^2-1-x^2}{2\sqrt{x}}}{x}=\frac{3x^2-1}{2x\sqrt{x}}$

(3)

$y'=\frac{2x+3}{2\sqrt{x^2+3x+5}}$

(4)

$y'=\frac{0-\dfrac{2x+2}{2\sqrt{x^2+2x+2}}}{\sqrt{x^2+2x+2}^2}=-\frac{x+1}{\sqrt{(x^2+2x+2)^3}}$