Question

Rezolvati exuatiile
a) x²-9x+18=0
b) 2x²-7x-4=0
c) 4x²-12x+9=0
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Answer 1

a)x²-9x+18=0

{a=1

{b=-9

{c=18

∆=b²-4ac=(-9)²-4•1•18=81-72=9

✓∆=✓9=3

x1=-b+✓∆ /2a = 9+3/2 = 12/2=6

x2=-b-✓∆ /2a = 9-3/2 = 6/2 =3

S={3;6}

b) 2x²-7x-4

{a=2

{b=-7

{c=-4

∆=b²-4ac=(-7)²-4•2•(-4)=49+32=81

√∆=✓81=9

x1=-b+✓∆ /2a = 7+9/2•2 = 16/4=4

x2=-b-✓∆ /2a = 7-9/2 = -2/2 =-1

S={1;4}

c) 4x²-12x+9=0

{a=4

{b=-12

{c=9

∆=b²-4ac=(-12)²-4•4•9=144-144=0

x1=x2 = -b/2a = 12/2•4 = 12/8 = 3/2

S={3/2}