Originally Posted byprime_66

is an under-determined system, so there will be

a free parameter in any solution. So we choose

so that it maximises the convenience of solving

the system in terms of it.

The constant on the RHS of the second equation is , as is the

coefficient of on the LHS. So setting allows

us to divide through by , and solve for in terms of .

Having found and in terms of

we just substitute these into the first equation to solve for

in terms of .

RonL