Question

\(x^2-78x+993=0\)

Answer 1

\(x^2-78x+993=0\\ \Leftrightarrow\left\{{}\begin{matrix}x=\dfrac{-\left(-78\right)+\sqrt{\left(-78\right)^2-4\cdot1\cdot993}}{2\cdot1}=39+4\sqrt{33}\\x=\dfrac{-\left(-78\right)-\sqrt{\left(-78\right)^2-4\cdot1\cdot993}}{2\cdot1}=39-4\sqrt{33}\end{matrix}\right.\)

Answer 2

\(x^2-78x+993=0\)

\(\Delta=\left(-78\right)^2-4.993\)

    \(=6084-3972=2112>0\)

`->` pt có 2 nghiệm

\(\left\{{}\begin{matrix}x_1=\dfrac{78+\sqrt{2112}}{2}=39+4\sqrt{33}\\X_2=\dfrac{78-\sqrt{2112}}{2}=39-4\sqrt{33}\end{matrix}\right.\)