$\"\"$

(a)

Find the sign of $\"\"$ .

Observe the graph:

The slope for the $\"\"$ direction becomes more steeper from the point $\"\"$ as moved along $\"\"$ -axis.

Therefore, the gradient is positive.

$\"\"$ is positive.

$\"\"$

(b)

Find the sign of $\"\"$ .

Observe the graph:

The slope for the $\"\"$ direction becomes more steeper towards negative from the point $\"\"$ as moved along $\"\"$ -axis.

Therefore, the gradient is negative.

Hence, $\"\"$ is negative.

$\"\"$

(a) $\"\"$ is positive.

(b) $\"\"$ is negative.