1.Rezolvati ecuatiile : a) 3x-1=-10
b) -2x+4=x-5
c) x+2 = x-1 .
3 4
d)2x 2x^{2} -5x+2=0

2.Adi si Cristi au impreuna 65lei,Cristi si Bogdan au impreuna 52 lei,iar Adi si Bogdan au impreuna 47 lei.Cati lei are fiecare ?

1

Răspunsuri

2014-05-17T16:48:17+03:00
1) a)3x-1=-10   3x=-10+1    3x=-9  x= -3

b) -2x+4=x-5
-2x-x=-5-4
-3x=-9
3x=9
x=3

c)4(x+2)=3(x-1)
4x+8=3x-3
4x-3x=-3-8
x=-11

d)a=2
b=-5
c=2

Δ= 25 -4*2*2= 25 -16=9

x1, x2= (-5 -/+ √9)/2*2=   (-5  -/+ 3)/4
x1=(-5+3)/4= - 2/4= -1/2
x2= (-5-3)/4= -8/4= -2

(x+1/2)(x+2)=0
x+1/2=0  x+2=0
x=-1/2   x=-2

a+c=65
c+b=52
a+b=47
2a+2b+2c=65+52+47
2(a+b+c)=164
a+b+c=82
b=82-65=17
a=82-52=30
c=82-47=35
Mersii,dar totusi nu inteleg la ex 2 de ce este 2a+2b+2c...
pt ca aduni ecuatiile