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Răspuns:
3.
a) -x²+2x=0
a=-1 ; b=2;c=0
∆=b²-4ac
∆=2²-4×(-1)×0
∆=4
[tex]x1= \frac{ - b + \sqrt{delta} }{2a } \\ x1 = \frac{ - 2 + \sqrt{4} }{2 \times ( - 1) } \\ x1 = \frac{ - 2 + 2}{ - 2 } \\ x1 = \frac{0}{ - 2} \\ x2 = \frac{ - 2 - 2}{ - 2} \\ x2 = \frac{ - 4}{ - 2} \\ x2 = 2[/tex]
b)
x²-4x-21=0
a=1;b=-4;c=-21
∆=16+84
∆=100
[tex]x1 = \frac{ 4 + \sqrt{100} }{2} \\ x1 = \frac{4 + 10}{2} \\ x1 = \frac{14}{2} \\ x1 = 7[/tex]
[tex]x2 = \frac{4 - \sqrt{100} }{2} \\ x2 = \frac{4 - 10}{2} \\ x2 = \frac{ - 6}{2} \\ x2 = - 3[/tex]
4
a)
y=2x+3
y=x²
=>
2x+3=x²
-x²+2x+3=0
a=-1;b=2;c=3
∆=2²+12
∆=4+12
∆=16
[tex]x1 = \frac{ - 2 + \sqrt{16} }{ - 2} \\ x1 = \frac{ - 2 + 4}{ - 2} \\ x1 = \frac{2}{ - 2} \\ x1 = - 1[/tex]
[tex]x2 = \frac{ - 2 - 4}{ - 2} \\ x2 = \frac{ - 6}{ - 2} \\ x2 = 3[/tex]
b este in poza
sper ca te-am ajutat! ʕ •ᴥ•ʔ