<span>x^{2} -2х+3=0</span>
<span /><span>Д=b²-4aс</span>
<span />D=4-4*1*3=4-12=-8(розв язків немає)
<span>2)х²-х-3=0</span>
<span /><span>Д=1-4*1*(-3)=1+12=13=√13</span><span />
<span>х1={1+√13)/2.</span>
<span>х2=(1-√13)/2.</span>
<span>3)-х²+6х-5=0</span>
<span>Д=36-4*(-1)*(-5)+36-20=16=4²</span>
<span>х1=(-6+4)/-2=1</span>
<span>х2=5</span>
<span>4)-х²=2х+3=0</span>
<span>Д=4-4*(-1)*3=16=4²</span>
<span>х1=(2+4)/-2=-3</span>
<span>х2=(2-4)/-2=1</span>
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