Question

Find the length of the curve y=3x^3/2 from x=0 to x=5/9

Answer 1

$y=3x^{3/2}\implies y'=\dfrac92x^{1/2}$

The length of the curve is

$L=\displaystyle\int_0^{5/9}\sqrt{1+\left(\dfrac92x^{1/2}\right)^2}\,\mathrm dx=\int_0^{5/9}\sqrt{1+\dfrac{81}4x}\,\mathrm dx=\dfrac{335}{243}$