$\"\"$

\

The equation is $\"\"$ at the point $\"\"$ .

\

The system of equations are $\"\"$ .

\

Substitute $\"\"$ in $\"\"$ .

\

$\"\"$

\

$\"\"$

\

$\"\"$

\

The equation is in the form of quadratic equation.

\

The general form of quadratic equation is $\"\"$ .

\

Here $\"\"$ , $\"\"$ and $\"\"$ .

\

There is one solution to the quadratic if the discriminant $\"\"$ equals to $\"\"$ .

\

Substitute corresponding values.

\

$\"\"$

\

$\"\"$

\

$\"\"$

\

$\"\"$ . $\"\"$

\

The tangent line $\"\"$ passes through the point $\"\"$ .

\

$\"\"$

\

$\"\"$

\

Substitute $\"\"$ in $\"\"$ .

\

$\"\"$

\

$\"\"$

\

$\"\"$

\

$\"\"$

\

$\"\"$

\

$\"\"$

\

Substitute $\"\"$ in $\"\"$ .

\

$\"\"$ .

\

Substitute $\"\"$ and $\"\"$ in $\"\"$ .

\

$\"\"$ .

\

Therefore, the line equation is $\"\"$ .

\

$\"\"$

\

The line equation is $\"\"$ .