(a)

Find the sign of .

Observe the graph:

The value of the function decreases at the point as -value increases from the point along -axis.

Hence, is negative.

(b)

Find the sign of .

Observe the graph:

The value of the function decreases at the point as -value increases from the point along -axis.

Hence, is negative.

(a) is negative.

(b) is negative.