Given two real numbers $a$ and $b$, consider $ab = a^2 - ab + b^2$. What is the value of 1?
(a) 1
(b) 0
(c) 2
(d) -2
(e) -1
The correct option is (a).

By setting $a=1$ and $b=0$ in $a=a^{2}-a b+b^{2}$, we obtain $1 \times 1^{2}-1 \times 0+0^{2}=1$.