Răspuns:
Explicație pas cu pas:
Ex29.
[tex]a=...=\dfrac{1}{1}-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+...+\dfrac{1}{42}-\dfrac{1}{43}=\dfrac{1}{1}-\dfrac{1}{43}=\dfrac{42}{43}\\b=...=\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{5}+...+\dfrac{1}{125}-\dfrac{1}{126}=\dfrac{1}{2}-\dfrac{1}{126}=\dfrac{62}{126}=\dfrac{31}{63}\\a:b=\dfrac{42}{43}:\dfrac{31}{63}=\dfrac{42*63}{43*31}= \dfrac{2646}{1333}[/tex]
