Tìm x : 1/2x+5/2=7/2x-3/4 (x-2/7)(x+3/4)=0 (2x+1/5)(-3/5x+4/7)=0 (-5/4x+3,25)[3/5-(-5/2x)]=0 23/08/2021 Bởi Ximena Tìm x : 1/2x+5/2=7/2x-3/4 (x-2/7)(x+3/4)=0 (2x+1/5)(-3/5x+4/7)=0 (-5/4x+3,25)[3/5-(-5/2x)]=0
Đáp án: $a)\dfrac{1}{2}x + \dfrac{5}{2} = \dfrac{7}{2}x – \dfrac{3}{4}$ $⇔\dfrac{1}{2}x – \dfrac{7}{2}x = -\dfrac{3}{4} – \dfrac{5}{2}$ $⇔ -3x = -\dfrac{13}{4}$ $⇔ x = -\dfrac{13}{4} : (-3) $ $⇔ x = \dfrac{13}{12}$ $\text{Vậy x = $\dfrac{13}{12}$}$ $b)(x – \dfrac{2}{7})(x+ \dfrac{3}{4}) = 0$ ⇔\(\left[ \begin{array}{l}x-\dfrac{2}{7}=0\\x+\dfrac{3}{4}=0\end{array} \right.\) ⇔\(\left[ \begin{array}{l}x=\dfrac{2}{7}\\x=-\dfrac{3}{4}\end{array} \right.\) $\text{Vậy x ∈ {$\dfrac{2}{7}$ ; -$\dfrac{3}{4}$ } }$ $c)(2x+\dfrac{1}{2})(-\dfrac{3}{5}x + \dfrac{4}{7}) = 0$ ⇔\(\left[ \begin{array}{l}2x+\dfrac{1}{5}=0\\-\dfrac{3}{5}x+\dfrac{4}{7}=0\end{array} \right.\) ⇔\(\left[ \begin{array}{l}x=-\dfrac{1}{10}\\x=\dfrac{20}{21}\end{array} \right.\) $\text{Vậy x ∈ { -$\dfrac{1}{10}$ ; $\dfrac{20}{21}$}}$ $d)(-\dfrac{5}{4}x + 3,25)[ \dfrac{3}{5}- (-\dfrac{5}{2}x)]=0$ $⇔(-\dfrac{5}{4}x + 3,25)(\dfrac{3}{5} + \dfrac{5}{2}x)=0$ ⇔\(\left[ \begin{array}{l}-\dfrac{5}{4}x +3,25=0\\\dfrac{3}{5}+\dfrac{5}{2}x=0\end{array} \right.\) ⇔\(\left[ \begin{array}{l}x=\dfrac{13}{5}\\x=-\dfrac{6}{25}\end{array} \right.\) $\text{Vậy x ∈ { $\dfrac{13}{5}$ ; -$\dfrac{6}{25}$}}$ Bình luận
Đáp án: Giải thích các bước giải: a/ $\frac{1}{2}x+\frac{5}{2}=\frac{7}{2}x-\frac{3}{4}$=> $\frac{1}{2}x-\frac{7}{2}x=-\frac{3}{4}-\frac{5}{2}$=> $-3x=-\frac{13}{4}$=> $x=\frac{13}{4}:3=\frac{13}{12}$b/ $(x-\frac{2}{7})(x+\frac{3}{4})=0$=> \(\left[ \begin{array}{l}x=\frac{2}{7}\\x=-\frac{3}{4}\end{array} \right.\)c/ $(2x+\frac{1}{5})(-\frac{3}{5}x+\frac{4}{7})=0$=>\(\left[ \begin{array}{l}2x=-\frac{1}{5}\\-\frac{3}{5}x=-\frac{4}{7}\end{array} \right.\) =>\(\left[ \begin{array}{l}x=-\frac{1}{10}\\x=\frac{20}{21}\end{array} \right.\)d/ $(-\frac{5}{4}x+3,25)[\frac{3}{5}-(-\frac{5}{2}x)]=0$=> $(-\frac{5}{4}x+3,25)(\frac{3}{5}+\frac{5}{2}x)=0$=>$\left[ \begin{array}{l}-\frac{3}{4}x=-3,25\\\frac{5}{2}x=-\frac{3}{5}\end{array} \right.$=> $\left[ \begin{array}{l}x=\frac{13}{3}\\x=-\frac{6}{25}\end{array} \right.$Chúc bạn học tốt !!! Bình luận
Đáp án:
$a)\dfrac{1}{2}x + \dfrac{5}{2} = \dfrac{7}{2}x – \dfrac{3}{4}$
$⇔\dfrac{1}{2}x – \dfrac{7}{2}x = -\dfrac{3}{4} – \dfrac{5}{2}$
$⇔ -3x = -\dfrac{13}{4}$
$⇔ x = -\dfrac{13}{4} : (-3) $
$⇔ x = \dfrac{13}{12}$
$\text{Vậy x = $\dfrac{13}{12}$}$
$b)(x – \dfrac{2}{7})(x+ \dfrac{3}{4}) = 0$
⇔\(\left[ \begin{array}{l}x-\dfrac{2}{7}=0\\x+\dfrac{3}{4}=0\end{array} \right.\)
⇔\(\left[ \begin{array}{l}x=\dfrac{2}{7}\\x=-\dfrac{3}{4}\end{array} \right.\)
$\text{Vậy x ∈ {$\dfrac{2}{7}$ ; -$\dfrac{3}{4}$ } }$
$c)(2x+\dfrac{1}{2})(-\dfrac{3}{5}x + \dfrac{4}{7}) = 0$
⇔\(\left[ \begin{array}{l}2x+\dfrac{1}{5}=0\\-\dfrac{3}{5}x+\dfrac{4}{7}=0\end{array} \right.\)
⇔\(\left[ \begin{array}{l}x=-\dfrac{1}{10}\\x=\dfrac{20}{21}\end{array} \right.\)
$\text{Vậy x ∈ { -$\dfrac{1}{10}$ ; $\dfrac{20}{21}$}}$
$d)(-\dfrac{5}{4}x + 3,25)[ \dfrac{3}{5}- (-\dfrac{5}{2}x)]=0$
$⇔(-\dfrac{5}{4}x + 3,25)(\dfrac{3}{5} + \dfrac{5}{2}x)=0$
⇔\(\left[ \begin{array}{l}-\dfrac{5}{4}x +3,25=0\\\dfrac{3}{5}+\dfrac{5}{2}x=0\end{array} \right.\)
⇔\(\left[ \begin{array}{l}x=\dfrac{13}{5}\\x=-\dfrac{6}{25}\end{array} \right.\)
$\text{Vậy x ∈ { $\dfrac{13}{5}$ ; -$\dfrac{6}{25}$}}$
Đáp án:
Giải thích các bước giải:
a/ $\frac{1}{2}x+\frac{5}{2}=\frac{7}{2}x-\frac{3}{4}$
=> $\frac{1}{2}x-\frac{7}{2}x=-\frac{3}{4}-\frac{5}{2}$
=> $-3x=-\frac{13}{4}$
=> $x=\frac{13}{4}:3=\frac{13}{12}$
b/ $(x-\frac{2}{7})(x+\frac{3}{4})=0$
=> \(\left[ \begin{array}{l}x=\frac{2}{7}\\x=-\frac{3}{4}\end{array} \right.\)
c/ $(2x+\frac{1}{5})(-\frac{3}{5}x+\frac{4}{7})=0$
=>\(\left[ \begin{array}{l}2x=-\frac{1}{5}\\-\frac{3}{5}x=-\frac{4}{7}\end{array} \right.\)
=>\(\left[ \begin{array}{l}x=-\frac{1}{10}\\x=\frac{20}{21}\end{array} \right.\)
d/ $(-\frac{5}{4}x+3,25)[\frac{3}{5}-(-\frac{5}{2}x)]=0$
=> $(-\frac{5}{4}x+3,25)(\frac{3}{5}+\frac{5}{2}x)=0$
=>$\left[ \begin{array}{l}-\frac{3}{4}x=-3,25\\\frac{5}{2}x=-\frac{3}{5}\end{array} \right.$
=> $\left[ \begin{array}{l}x=\frac{13}{3}\\x=-\frac{6}{25}\end{array} \right.$
Chúc bạn học tốt !!!