Odpowiedź:
[tex]f(x)=2x^2-5x-18\\\\2x^2-5x-18=0\\\\a=2\ \ ,\ \ b=-5\ \ ,\ \ c=-18\\\\\Delta=b^2-4ac=(-5)^2-4\cdot2\cdot(-18)=25+144=169\\\\\sqrt{\Delta}=\sqrt{169}=13\\\\x_{1}=\frac{-b-\sqrt{\Delta}}{2a}=\frac{-(-5)-13}{2\cdot2}=\frac{5-13}{4}=\frac{-8}{4}=-2\\\\x_{2}=\frac{-b+\sqrt{\Delta}}{2a}=\frac{-(-5)+13}{2\cdot2}=\frac{5+13}{4}=\frac{18}{4}=\frac{9}{2}\\\\\\f(x)=a(x-x_{1})(x-x_{2})\\\\f(x)=2(x-(-2))(x-\frac{9}{2})\\\\f(x)=2(x+2)(x-\frac{9}{2})[/tex]
