Analyzing the Setup
When you look at the expression v=∣z∣2+∣z−3∣2+∣z−6i∣2, it is easy to see an algebraic mess. However, in the complex plane, the modulus ∣z−z1∣ represents the distance between two points.
Therefore, the expression v is the sum of the squared distances from a variable point z to three fixed vertices: 0, 3, and 6i.
There is an elegant theorem in geometry: the sum of the squares of the distances from any point to the vertices of a triangle is minimized at the centroid. The centroid acts as the "center of mass" of the triangle, representing the point of perfect balance.
Finding the Balance Point
Since z0 is the centroid, we find it by calculating the arithmetic mean of the three vertices:
This is our minimizing point. Now, we substitute z0=1+2i back into the original expression to find the minimum value v0:
v0=∣1+2i∣2+∣1+2i−3∣2+∣1+2i−6i∣2
Breaking this down, we evaluate the individual components:
v0=∣1+2i∣2+∣−2+2i∣2+∣1−4i∣2
Calculating these magnitudes yields:
(12+22)+((−2)2+22)+(12+(−4)2)=5+8+17=30
Thus, we have determined that v0=30.
The Algebraic Finale
We now evaluate the final expression: ∣2z02−zˉ03+3∣2+v02. First, we compute the powers of z0:
z02=(1+2i)2=1+4i−4=−3+4i
Next, we find the cube of the conjugate zˉ0=1−2i:
zˉ03=(1−2i)3=1−3(2i)+3(2i)2−(2i)3=1−6i−12+8i=−11+2i
Now, we assemble the internal expression:
2z02−zˉ03+3=2(−3+4i)−(−11+2i)+3
Finally, we calculate the squared magnitude and add v02:
∣8+6i∣2+302=(82+62)+900=100+900=1000
The final result is 1000.