Question

AxB=16
A+B=40
aflati:
2x($\frac{1}{B} + \frac{1}{A}$)

Answer 1

$2 \cdot ( \frac{1}{b}+ \frac{1}{a})=2 \cdot ( \frac{a}{ab}+ \frac{b}{ab})=2 \cdot \frac{a+b}{ab}=2 \cdot \frac{40}{16}=5.$