Question

Fie numerele rationale a,b,c,d.
       Daca a=5 supra 6, b+c= 7 supra 20 si c-d= 1 supra 24, calculati a*b+2*a*c-a*d. 

Answer 1

$ab+2ac-ad=a(b+2c-d)=a\left[(b+c)+(c-d)\right]=\\=\displaystyle\frac{5}{6}\left(\frac{7}{20}+\frac{1}{24}\right)=\displaystyle\frac{5}{6}\cdot\frac{47}{120}=\frac{47}{144}$