$\"\"$

The curve is $\"\"$ , $\"\"$ .

Consider $\"\"$ .

Differentiate the above equation with respect to $\"\"$ .

$\"\"$ .

Consider $\"\"$ .

Differentiate the above equation with respect to $\"\"$ .

$\"\"$ .

$\"\"$

Now find $\"\"$ .

$\"\"$

Now find $\"\"$ .

$\"\"$ .

Again differentiate the above equation with respect to $\"\"$ .

$\"\"$

Since $\"\"$ because of domain of function in, $\"\"$ , so the curve concave upwards for $\"\"$ .

$\"\"$

The curve concave upwards for $\"\"$ .