[tex]9x^2=17\ \ \ |:9\\\\x^2=\dfrac{17}{9}\to x=\pm\sqrt{\dfrac{17}{9}}\\\\\boxed{Answer:\ x\approx-1.37\ \vee\ x=1.37}[/tex]
[tex]ax^2+bx+c=0\\\\\Delta=b^2-4ac\\\\if\ \Delta > 0\ then\ the\ equation\ has\ 2\ solutions\\if\ \Delta=0\ then\ the\ equation\ has\ 1\ solution\\if\ \Delta < 0\ then\ the\ equation\ has\ no\ solution[/tex]
[tex]x^2+5x+7=0\\a=1;\ b=5;\ c=7\\\\Delta=5^2-4\cdot1\cdot7=25-28=-3 < 0\\\\\boxed{Answer:\ 0}[/tex]
[tex]5y^2-8y=2\ \ \ |-2\\\\5y^2-8y-2=0\\\\a=5;\ b=-8;\ c=-2\\\\b^2-4ac=(-8)^2-4\cdot5\cdot(-2)=64+40=104\\\\\sqrt{b^2-4ac}=\sqrt{104}\approx10.198\\\\y_1=\dfrac{-b-\sqrt{b^2-4ac}}{2a};\ y_2=\dfrac{-b+\sqrt{b^2-4ac}}{2a}\\\\y_1=\dfrac{-(-8)-10.198}{2\cdot5}\approx-0.22\\\\y_2=\dfrac{-(-8)+10.198}{2\cdot5}\approx1.82\\\\\boxed{Answer:\ 1.82,\ -0.22}[/tex]
