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Parent graph:The simplest form of the given function is called the parent function of that function and the graph of the parent function is called parent graph.

Domain: The set of all possible values for which given function defined is called domain.

Range: The set of all possible values of the given function is called range.

The given function is: $y=−\frac{1}{5}\sqrt{x}$

In order to graph a function, find few co-ordinates by substituting values of ‘$x$’ and find finding the respective values of ‘$y$’.

$\begin{array}{c}\text{¹ó´Ç°ù â¶Ä‰}x=0,\\ y=−\frac{1}{5}\sqrt{0}\\ =−\frac{1}{5}\left(0\right)\\ =0\end{array}$

$\begin{array}{c}\text{¹ó´Ç°ù â¶Ä‰}x=1,\\ y=−\frac{1}{5}\sqrt{1}\\ =−\frac{1}{5}\left(1\right)\\ =−0.2\end{array}$

$\begin{array}{c}\text{¹ó´Ç°ù â¶Ä‰}x=4,\\ y=−\frac{1}{5}\sqrt{4}\\ =−\frac{1}{5}\left(2\right)\\ =−0.4\end{array}$

$\begin{array}{c}\text{¹ó´Ç°ù â¶Ä‰}x=9,\\ y=−\frac{1}{5}\sqrt{9}\\ =−\frac{1}{5}\left(3\right)\\ =−0.6\end{array}$

$\begin{array}{c}\text{¹ó´Ç°ù â¶Ä‰}x=16,\\ y=−\frac{1}{5}\sqrt{16}\\ =−\frac{1}{5}\left(4\right)\\ =−0.8\end{array}$

Plot these co-ordinates on a coordinate plane and join those points to get the required graph.

The parent function of$y=−\frac{1}{5}\sqrt{x}$ is the simplest square root function.

That is,$y=\sqrt{x}$

Using graphing calculator, the graph of parent function$y=\sqrt{x}$ is given below.

Note: Since the parent function is just used for comparison, it is graphed using graphing calculator.

Coefficient of$\sqrt{x}$ is $−\frac{1}{5}$.

The absolute value of coefficient of $\sqrt{x}$is $\frac{1}{5}$.

As $\frac{1}{5}$is less than 1. The graph is a vertical compression of the parent graph $y=\sqrt{x}$.

Also as the coefficient $−\frac{1}{5}$of $\sqrt{x}$ is negative, the graph is a reflection across the $x$-axis.

Therefore, on comparison with the parent graph, the graph $y=−\frac{1}{5}\sqrt{x}$ a vertical compression and a reflection across $x$-axis.

Since ‘$x$’ is inside the root, the values inside the root must be positive.

Therefore, values of $x$ is all positive real numbers including zero.

That is, $xâ‰\yen 0,\text{ â¶Ä‰â¶Ä‰}⇒x∈[0,∞)$.

Therefore, domain: $[0,∞)$

In $y=−\frac{1}{5}\sqrt{x}$, the square root of $x$is multiplied by $−\frac{1}{5}$.

As square root is always positive, the least value it takes is zero.

Therefore, find the least value of $y$by substituting $x=0$in $y=−\frac{1}{5}\sqrt{x}$.

$\begin{array}{c}y=−\frac{1}{5}\left(\sqrt{0}\right)\\ =−\frac{1}{5}\left(0\right)\\ =0\end{array}$

In $y=−\frac{1}{5}\sqrt{x}$, the coefficient of $\sqrt{x}$is negative.

Therefore, $y$takes all the values in real numbers which are less than or equal to zero.

Therefore,$y≤0,\text{ â¶Ä‰â¶Ä‰}⇒y∈(−∞,0]$

Therefore, Range:$(−∞,0]$