(x-9)(x+9)/x(x²+18+81)=
(x-9)(x+9)/x(x+9)²=
(x-9)/x(x+9)
a)DM,il,aflam,direct,din,ΔDCM,dr.
Stim,ca,CM=20(M,este,mijl.lui,BC),CD=40
=>DM²=CD²+CM²
DM²=400+1600=>DM²=2000=>DM=20√5
b)In,tr.dr.DAN,AD²+AN²=DN²;1600+X²=DN²=2000+MN²(ΔDMN,dr-ipoteza)
In,tr,dr,NBM,NB²+BM²=MN²;(40-X)²+400=MN²
1600+X²=2000+(40-X)²+400
1600+X²=2000+1600-80X+X²+400
2400=80X=>X=30
c)A=1600m²
A(ΔDMN)=10√5x20√5/2=500m²
1600__________100%
500___________a
a=50000/1600=>a=31,25%