Question

4x² - 7x + 2 = 0 ?????

Answer 1

\(\left[{}\begin{matrix}x=\dfrac{7-\sqrt{17}}{8}\\x=\dfrac{7+\sqrt{17}}{8}\end{matrix}\right.\)

Answer 2

\(\Leftrightarrow\left(x-2\right)\left(4x+1\right)=0\)

\(\Leftrightarrow x-2=0\)                  hay          \(4x+1=0\)

\(\Leftrightarrow x=2\)                                      \(\Leftrightarrow\)  \(4x=-1\)

                                                     \(\Leftrightarrow x=-\dfrac{1}{4}\)

Vậy \(S=\left\{2,-\dfrac{1}{4}\right\}\)

Answer 3

\(\Delta=\left(-7\right)^2-4\cdot4\cdot2=49-32=17\)

Do đó: Phương trình có hai nghiệm phân biệt là:

\(\left\{{}\begin{matrix}x_1=\dfrac{7-\sqrt{17}}{8}\\x_2=\dfrac{7+\sqrt{17}}{8}\end{matrix}\right.\)