Question:
The approximate value of $(33)^{1 / 5}$ is
(a) 2.0125
(b) 2.1
(c) 2.01
(d) none of these
Solution:
(a) 2.0125
Consider the function $y=f(x)=x^{\frac{1}{5}}$.
Let :
$x=32$
$x+\Delta x=33$
$\Rightarrow \Delta x=1$
$y=(x)^{\frac{1}{5}}$
For $x=32$,
$y=2$
$\mathrm{AlsO}, \frac{d y}{d x}=\frac{1}{5(x)^{\frac{4}{5}}}$
$\Rightarrow\left(\frac{d y}{d x}\right)_{x=32}=\frac{1}{80}$
$\Rightarrow \Delta y=d y=\frac{d y}{d x} d x=\frac{1}{80} \times 1=0.0125$
$\therefore(33)^{\frac{1}{5}}=y+\Delta y=2.0125$