SVP!!!!!!!!!!!! Sachant que a = -2/21et b =5/-7' calcule a/b ;b/a ; a x b ; a +b et a -b tu donneras les résultats sous la forme d'une fractions irreductible
a/b = (-2/21) /( 5/-7) = (2/21) *(7/5) =2/15
b/a =( 5/-7) / (-2/21) =(5/7)*(21/2) =15/2
a*b =(-2/21) *( 5/-7) = (2*5)/(7*21) =10/147
a -b=(-2/21) -( 5/-7) = -2/21 + 5/7 = -2/21 + 15/21 = 13/21