Question

Am nevoie urgent de rezolvarea la exercițiile 3 și 4.

Answer 1

4.
a/3=b/5=c/7

a)a+c=2b
a/3=b/5; 5a=3b; a=3b/5
b/5=c/7; 7b=5c ; c=7b/5
a+c=3b/5+7b/5=10b/5= 2b
 
b)a²-b²+c²=297

9b²/25-b²+49b²/25= 33b²/25
33b²/25=297
33b²=297*25
33b²=7425
b²=7425:33
b²=225
b=√225=15;

a=3b/5; a=3*15 /5; a=45/5; a=9
c=7b/5; c= 7*15/5; c=105/5; c=21

verificare
a²-b²+c²=81-225+441=297

Ex3:3) 76:x=C1 r1
93:x=C2r3
76=xC1+1
93=xC2+3
76-1=xC1;  xC1=75
93-3=xC2;  xC2=90;  x fiind cuprins intre 1 si 9

75= 3*5²
90= 2*3²*5, x≠2,  x≠ 5²; x≠3*2 ; x≠9

incercam x= 5
76 :5= 15 rest 1
93:5=18, rest 3

S: x=5