Reflection of P(a, b) in x-axis followed by the reflection in y-axis is :

1. (a, b)

2. (-a, b)

3. (a, -b)

4. (-a, -b)

We know that,

On reflecting in x-axis the sign of y co-ordinate changes.

Let on reflection in x-axis the point P(a, b) becomes P'.

P(a, b) ⇒ P'(a, -b).

We know that,

On reflecting in y-axis the sign of x co-ordinate changes.

On reflection in y-axis point P'(a, -b) becomes P".

P'(a, -b) ⇒ P"(-a, -b).

Hence, Option 4 is the correct option.