Expanding the equations we have

Collecting like terms we have

Dividing the last equation by 4 we have the required equations

| (3) |

| (4) |

Multiplying (

4) by 3 we have

| (5) |

Subtract (

3) from (

5) and we have

Substituting into (

4) we have

Check in (

1) and we have

Hence