Hi.

ok you have that and .

Now substitute the first into the second. This gives:

so

Now differentiate and equate to zero to find the turning point

so

(you can clarify that this is a minimum by differentiating again and seeing it is positive)

Now plug this into to get as the min value.

Now plug back into to get

so are the values of x and y where the minimum occurs.

HTH

Si.