5-x, x+7, 3x+11 sunt in progresie geometrica
5-x/x+7=x+7/3x+11 =>
=> (x+7) la puterea a 2a=(5-x)*(3x+11)
x la puterea a 2a+14x+49=15x la puterea a 2a+55-3x la puterea a 2a-11x
x la puterea a 2a+14x+49-15x la puterea a 2a-55+3x la puterea a 2a+11x=0
-11x la puterea a 2a+25-6=0
a=-11 ; b=25 ; c=-6 => DELTA = b la puterea a 2a-4ac=625-4*(-11)*(-6)=625-264=361 => √361=19
x1=-b+√Δ/2a=-25+19/-22=-6/-22=-3/-11
x2=-b-√Δ/2a=-25-19/-22=-44/-22=2
Sper ca te-am ajutat.. Coroana?