B3. The area of the triangle enclosed by the line with the positive half-axes of the coordinate axes is equal to 1. The line passes through the point $A\left(1, \frac{1}{2}\right)$. Write its equation.
B3. The straight line intersects the coordinate axes at points $(m, 0)$ and $(0, n)$. The equation of the line is then $\frac{x}{m}+\frac{y}{n}=$ 1. Since the area of the triangle is $1=\frac{m n}{2}$, it follows that $n=\frac{2}{m}$ and $\frac{x}{m}+\frac{m y}{2}=1$. Considering that the point $A\left(1, \frac{1}{2}\right)$ lies on the line, we get $\frac{1}{m}+\frac{m}{4}=1$ or $0=m^{2}-4 m+4=(m-2)^{2}$. Therefore, $m=2$, and the equation of the line is $\frac{x}{2}+y=1$.