Răspuns:
Explicație pas cu pas:
b = 2a/3
c = (a + b)*7/4 = (a + 2a/3)*7/4 = 5a/3 * 7/4 = 35a/12
(ab + ac)/(b^2 + c^2) = ?
ab = 2a^2/3
ac = 35a^2/12
ab + ac = 2a^2/3 + 35a^2/12 = 8a^2/12 + 35a^2/12 = 43a^2/12
b^2 = 4a^2/9
c^2 = 1225a^2/144
b^2 + c^2 = 4a^2/9 + 1225a^2/144 = 64a^2/144 + 1225a^2/144 = 1289a^2/144
(ab + ac)/(b^2 + c^2) = 43a^2/12 : 1289a^2/144 = 43a^2/12 * 144/1289a^2 =
43*12/1289 = 516/1289
