Question

Fie numerele:
a=√28-√72+√80;
b= -√63 + √162 - √180;
c= √3-1 / √3 + √5-√3 / √15 + √7-√5 / √35 + √9-√7 / √63;

Aratati ca numerele a:b si c sunt numere rationale opuse.

Answer 1

a=√28-√72+√80=2√7-6√2+4√5

b= -√63 + √162 - √180=-3√7+9√2-6√5

c= √3-1 / √3 + √5-√3 / √15 + √7-√5 / √35 + √9-√7 / √63=(3-√3/)3+(5√3-3√5)/15+(7√5-5√7)/35+(9√7-21)/63=(315-105√3+105√3-63√5+63√5-45√7+45√7-189)/315=126/315=2/5




a:b=
(2√7-6√2+4√5):(-3√7+9√2-6√5)=(2√7-6√2+4√5)*(-3√7+9√2-6√5)/195=-2/5