Hej!
[tex]-2x^2-7x+4\leq0\\\\a=-2, \ b=-7, \ c=4\\\\\Delta=b^2-4ac\rightarrow(-7)^2-4\cdot(-2)\cdot4=49+32=81\\\\\sqrt{\Delta}=\sqrt{81}=9\\\\x_1=\frac{-b-\sqrt{\Delta}}{2a}\rightarrow\frac{-(-7)-9}{2\cdot(-2)}=\frac{7-9}{-4}=\frac{-2}{-4}=\frac{1}{2}\\\\x_2=\frac{-b+\sqrt{\Delta}}{2a}\rightarrow\frac{-(-7)+9}{2\cdot(-2)}=\frac{7+9}{-4}=-\frac{16}{4}=-4\\\\x\in(-\infty;-4\rangle\cup\langle\frac{1}{2};+\infty)[/tex]
a < 0, ramiona paraboli skierowane do dołu, kółeczka zamalowane
Pozdrawiam! - Julka
