### Instruction: Find all values of $z$ such that $z^4 - 4z^2 + 3 = 0$.  Enter all the solutions, separated by commas.### Response: So we have $z^4-4z^2+3=0$.
Let $y=z^2$.
Then $y^2-4y+3=0$.
So $y=1$ or $y=3$.
And $z^2=1$ or $z^2=3$.
So $z=\pm 1$ or $z=\pm \sqrt{3}$.
That's four solutions.