Question

1. Calculati :
a) ( 7 supra 4 + 1 supra 6 )*12 supra 13
b) ( 5 supra 6 - 1 supra 3 ) : 1 supra 4
c) media ponderata a numerelor a=2,7 si b=4,8(6) cu ponderile 4 si 6. Va rog...
2. Rezolvati in Q+ ecuatiile :
a) 3,5x + 3,35 = 20,85
b) 0,8(x + 0,2 ) = 4,96
3. Rezolvati ecuatia :
x+3 supra 5 +x+5 supra 6 + x + 7 supra 7 = 6

Answer 1

a) ( 7/4 + 1/6 )x12/13=[(7x3+1x2)/12]x12/13=24/12x12/13=24/13

b) ( 5/6 - 1/3 ) : 1/4=[(5-2)/6]x4=12/6=2

c)a=2,7=27/10
 b=4,8(6)(486-48)/90=438/90simplif=219/45=73/15
Mp=(4x27/10+6x73/15)/(4+6)=(10,8+29,2)/10=40/10=4

2) a) 3,5x + 3,35 = 20,85
3,5x=20,85-3,35
3,5x=17,5
x=17,5/13,5=175/10:135/10=175/10·10/135=175/135=35/27=1,(296)
x=1,(296)

b) 0,8(x + 0,2 ) = 4,96
0,8x+0,16=4,96
0,8x=4,96-0,16
0,8x=4,8
x=4,8/0,8
x=6

3. Rezolvati ecuatia :
(x+3)/5 +(x+5)/6 + (x + 7)/7 = 6
(42x+3·42+35x+35·5+30x+7·30)/210=6
107x+511=6·210
107x=1260-511
107=749
x=749/107
x=7