When b²−4ac=0 there is one real root.
When b²−4ac>0 there are two real roots.
When b²−4ac<0 no real roots or two complex roots
First equation
-x²-4x+7
![\begin{gathered} b^(2)-4ac \\ \mleft(-4\mright)^2-4\mleft(-1\mright)\cdot\: 7 \\ 16+28=44 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/high-school/7du6hgw4n123m26clpt60p1xppfljvf9zo.png)
b²−4ac>0, then equation -x²-4x+7 has two real roots.
Second equation
-2x²+9x-11
![\begin{gathered} b^(2)-4ac \\ 9^2-4\mleft(-2\mright)\mleft(-11\mright) \\ 81-88=-7 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/high-school/19rz82ttobocrop3cog7bn4jpgjta6qtvi.png)
b²−4ac<0, then equation -2x²+9x-11 has two complex roots.
![x1=(9)/(4)-i(√(7))/(4),\: x2=(9)/(4)+i(√(7))/(4)](https://img.qammunity.org/2023/formulas/mathematics/high-school/7r7nydm64vkiw5tsdrix9ydtv2ce2b48zq.png)
Third equation
3x²-6x+3
![\begin{gathered} b^(2)-4ac \\ \mleft(-6\mright)^2-4\cdot\: \: 3\cdot\: \: 3 \\ 36-36=0 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/high-school/jyb1gn9t8q0uzczon8iem3iob223u9dx5g.png)
b²−4ac=0, then equation 3x²-6x+3 has one root.