Question

Stiind ca a+b=4 si a.b=2,calculati 1/a+1/b.

Answer 1

$\frac{1}{a} + \frac{1}{b} = \frac{a+b}{ab} = \frac{4}{2} =2$

Answer 2

a+b=4
axb=2
1/a+1/b=  (amplific prima fractie cu b si a doua cu a) 
=b/ab+a/ab=
=(b+a)/ab=    (am inlocuit suma si produsul numerelor)
=4/2=
=2