a) \(\Delta=b^2-4ac=\left(-7\right)^2-4\cdot2\cdot\left(-3\right)=49+24=73\)
Vì \(\Delta>0\) nên phương trình có hai nghiệm là:
\(\left\{{}\begin{matrix}x_1=\frac{-b+\sqrt{\Delta}}{2a}\\x_2=\frac{-b-\sqrt{\Delta}}{2a}\end{matrix}\right.\Leftrightarrow\left\{{}\begin{matrix}x_1=\frac{7+\sqrt{73}}{2\cdot2}=\frac{7+\sqrt{73}}{4}\\x_2=\frac{7-\sqrt{73}}{2\cdot2}=\frac{7-\sqrt{73}}{4}\end{matrix}\right.\)
Vậy: \(S=\left\{\frac{7+\sqrt{73}}{4};\frac{7-\sqrt{73}}{4}\right\}\)
\(\Delta=\left(-7\right)^2-4.2.\left(-3\right)=73>0\)
⇒ pt có 2 nghiệm phân biệt
\(\Rightarrow\left\{{}\begin{matrix}x_1=\frac{7+\sqrt{73}}{4}\\x_2=\frac{7-\sqrt{73}}{4}\end{matrix}\right.\)
