Toán Lớp 7: |x+5|-6=9 $\frac{2}{3}$ + $\frac{5}{3}$x = $\frac{5}{7}$

TRẢ LỜI

1. Bài làm:

   a, |x + 5| – 6 = 9

   <=> |x + 5| = 15

   <=> $\left[\begin{matrix} x + 5 = 15\\ x + 5 = -15\end{matrix}\right.$

   <=> $\left[\begin{matrix} x = 10\\ x = -20\end{matrix}\right.$

   b, $\dfrac{2}{3}$ + $\dfrac{5}{3}$ x = $\dfrac{5}{7}$

   <=> $\dfrac{5}{3}$ x = $\dfrac{5}{7}$ – $\dfrac{2}{3}$

   <=>  $\dfrac{5}{3}$ x = $\dfrac{15}{21}$ – $\dfrac{14}{21}$

   <=> $\dfrac{5}{3}$ x = $\dfrac{1}{21}$

   <=> x = $\dfrac{3}{105}$

   <=> x = $\dfrac{1}{35}$

   @Enk

   #BTS

   Trả lời
2. Lời giải chi tiết:

   a) |x+5|-6=9

   =>|x+5|=9+6

   =>|x+5|=15

   =>\(\left[ \begin{array}{l}x+5=15\\x+5=-15\end{array} \right.\)

   =>\(\left[ \begin{array}{l}x=10\\x=-20\end{array} \right.\)

   Vậy x=10 hoặc x=-20

   b) 2/3+5/3x=5/7

   =>5/3x=5/7-2/3

   =>5/3x=1/21

   =>x=1/21:5/3

   =>x=1/35

   Vậy x=1/35

   Trả lời