Question

Answer 1

\(\Delta=\left(-1\right)^2-4.1.\left(-7\right)=1+28=29\)

\(\Rightarrow\left\{{}\begin{matrix}x_1=\dfrac{-\left(-1\right)+\sqrt{29}}{2.1}=\dfrac{1+\sqrt{29}}{2}\\x_2=\dfrac{-\left(-1\right)-\sqrt{29}}{2.1}=\dfrac{1-\sqrt{29}}{2}\end{matrix}\right.\)

Answer 2

Answer 3

\(\Delta=b^2-4ac=\left(-1\right)^2-4.\left(-7\right)=29>0\)

=> Pt có 2 nghiệm pb

\(x_1=\dfrac{-b+\sqrt{\Delta}}{2a}=\dfrac{1+\sqrt{29}}{2}\)

\(x_2=\dfrac{-b-\sqrt{\Delta}}{2a}=\dfrac{1-\sqrt{29}}{2}\)