43. Given $a>0, b>0$, and $\frac{1}{a}+\frac{2}{b}=1$.
(1) Find the minimum value of $a+b$;
(2) If line $l$ intersects the $x$-axis and $y$-axis at points $A(a, 0)$, $B(0, b)$, respectively, find the minimum value of the area of $\triangle O A B$.
43. (1) $3+2 \sqrt{2} ;(2) S_{\min }=4$