Explanation:

Initial Profit and Loss Sharing Ratio:
Ram Raj, and Rohan are partners sharing profits and losses in the ratio of 4:3:2 respectively. This means that they share the profits and losses in the following manner:
- Ram Raj receives 4/9th of the profits and losses.
- Rohan receives 3/9th of the profits and losses.
- The remaining partner receives 2/9th of the profits and losses.

New Profit and Loss Sharing Ratio:
As of April 1, 2017, they have decided to share the profits and losses in the ratio of 2:3:4. This means that they share the profits and losses in the following manner:
- Ram Raj receives 2/9th of the profits and losses.
- Rohan receives 3/9th of the profits and losses.
- The remaining partner receives 4/9th of the profits and losses.

Impact on Partnership:
The change in the profit and loss sharing ratio will have the following impact on the partnership:
- The partners will now share the profits and losses in a different manner.
- The partner who was previously receiving the lowest share of profits and losses will now receive the highest share.
- The partner who was previously receiving the highest share of profits and losses will now receive the lowest share.
- The change in profit and loss sharing ratio will affect the distribution of profits and losses among the partners.
- The partners will need to adjust their contributions and responsibilities in order to ensure that the new profit and loss sharing ratio is equitable and fair.

Conclusion:
In conclusion, Ram Raj and Rohan have changed their profit and loss sharing ratio from 4:3:2 to 2:3:4 with effect from 1st April 2017. This change will have an impact on their partnership and they will need to adjust their contributions and responsibilities accordingly.