Toán cúiiiiiii 20 lun nè nhanh thì lụm nha 3x^2+5x-7=0 21/10/2021 By Kaylee cúiiiiiii 20 lun nè nhanh thì lụm nha 3x^2+5x-7=0
Đáp án: \(\left[ \begin{array}{l}x=\frac{-5 – √109}{6} \\x=\frac{-5 + √109}{6} \end{array} \right.\) Giải thích các bước giải: 3x² + 5x – 7 = 0 ⇔ \(\left[ \begin{array}{l}x=\frac{-5 – √109}{6} \\x=\frac{-5 + √109}{6} \end{array} \right.\) Trả lời
$3x² +5x -7 = 0$ $⇔ (\sqrt{3}x + \dfrac{5\sqrt{3}}{6})² – \dfrac{109}{12} = 0$ $⇔ (\sqrt{3}x + \dfrac{5\sqrt{3}}{6} – \sqrt{\dfrac{109}{12}}).(\sqrt{3}x + \dfrac{5\sqrt{3}}{6} + \sqrt{\dfrac{109}{12}}) = 0$ $⇔ \left[ \begin{array}{l}\sqrt{3}x + \dfrac{5\sqrt{3}}{6} – \sqrt{\dfrac{109}{12}}=0\\\sqrt{3}x + \dfrac{5\sqrt{3}}{6} + \sqrt{\dfrac{109}{12}}=0\end{array} \right. ⇔ \left[ \begin{array}{l}x=\dfrac{-5 + \sqrt{109}}{6}\\x=\dfrac{-5 – \sqrt{109}}{6}\end{array} \right.$ $\text {Vậy S = {$\dfrac{-5 – \sqrt{109}}{6}$; $\dfrac{-5 + \sqrt{109}}{6}$}}$ Trả lời
Đáp án:
\(\left[ \begin{array}{l}x=\frac{-5 – √109}{6} \\x=\frac{-5 + √109}{6} \end{array} \right.\)
Giải thích các bước giải:
3x² + 5x – 7 = 0
⇔ \(\left[ \begin{array}{l}x=\frac{-5 – √109}{6} \\x=\frac{-5 + √109}{6} \end{array} \right.\)
$3x² +5x -7 = 0$
$⇔ (\sqrt{3}x + \dfrac{5\sqrt{3}}{6})² – \dfrac{109}{12} = 0$
$⇔ (\sqrt{3}x + \dfrac{5\sqrt{3}}{6} – \sqrt{\dfrac{109}{12}}).(\sqrt{3}x + \dfrac{5\sqrt{3}}{6} + \sqrt{\dfrac{109}{12}}) = 0$
$⇔ \left[ \begin{array}{l}\sqrt{3}x + \dfrac{5\sqrt{3}}{6} – \sqrt{\dfrac{109}{12}}=0\\\sqrt{3}x + \dfrac{5\sqrt{3}}{6} + \sqrt{\dfrac{109}{12}}=0\end{array} \right. ⇔ \left[ \begin{array}{l}x=\dfrac{-5 + \sqrt{109}}{6}\\x=\dfrac{-5 – \sqrt{109}}{6}\end{array} \right.$
$\text {Vậy S = {$\dfrac{-5 – \sqrt{109}}{6}$; $\dfrac{-5 + \sqrt{109}}{6}$}}$