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12. Rezolvaţi în R ecuațiile:
a) 2x²+x-3 = 0;
d) 2x²-5x + 2 = 0;
g) 3x² + x - 2 = 0;
b) 2x²-x-15 = 0;
e) 2x² + 3x + 1 = 0;
h) 3x² + 4x-7= 0;
c) 3x²-5x+2=0;
f) 2x²-x-3=0;
i) 2x²+x-1=0.


Răspuns :

Răspuns:

a)

delta = 1^2 - 4•2•(-3) = 25 => rad.delta = 5

x1 = (-1-5)/4 = -6/4 = -3/2

x2 = (-1+5)/4 = 1

d)

delta = (-5)^2 - 4•2•2 = 9 => rad.delta = 3

x1 = (5-3)/4 = 1/2

x2 = (5+3)/4 = 2

g)

delta = 1^2 - 4•3•(-2) = 25 => rad.delta = 5

x1 = (-1-5)/6 = -1

x2 = (-1+5)/6 = 2/3

b)

delta = (-1)^2 - 4•2•(-15) = 121 => rad.delta = 11

x1 = (1-11)/4 = -5/2

x2 = (1+11)/4 = 3

e)

delta = 3^2 - 4•2•1 = 1 => rad.delta = 1

x1 = (-3-1)/4 = -1

x2 = (-3+1)/4 = -1/2

h)

delta = 4^2 - 4•3•(-7) = 100 => rad.delta = 10

x1 = (-4-10)/6 = -7/3

x2 = (-4+10)/6 = 1

c)

delta = (-5)^2 - 4•3•2 = 1 => rad.delta = 1

x1 = (5-1)/6 = 2/3

x2 = (5+1)/6 = 1

f)

delta = (-1)^2 - 4•2•(-3) = 25 => rad.delta = 5

x1 = (1-5)/4 = -1

x2 = (1+5)/4 = 3/2

i)

delta = 1^2 - 4•2•(-1) = 9 => rad.delta = 3

x1 = (-1-3)/4 = -1

x2 = (-1+3)/4 = 1/2