Question

51.Fie a, b, c, d patru numere reale astfel incât a + b = rad5+ rad7 si c+d= rad5-rad7 .
Calculati ac + bd + ad + bc.
URGENT VA ROGGG DAU COROANA

Answer 1

Răspuns:

$ac + bd + ad + bc = a(c + d) + b(c + d) = (c + d)(a + b)$

$( \sqrt{5} - \sqrt{7} )( \sqrt{5} + \sqrt{7} ) = 5 - 7 = ( - 2)$