Tìm x : `b) |3/2 x + 1/9| + |5/7 y-1/2|=0`

2 bình luận về “Tìm x : `b) |3/2 x + 1/9| + |5/7 y-1/2|=0`”

1. b) |3/2x + 1/9 | + | 5/7 y – 1/2 | = 0 

   Vì |3/2x + 1/9 | ≥ 0 ∀ x ; | 5/7 y – 1/2 | ≥ 0 ∀ y

   => |3/2x + 1/9 | + | 5/7 y – 1/2 | ≥ 0 ∀ x , y

   Mà |3/2x + 1/9 | + | 5/7 y – 1/2 | = 0 

   =>$\{\begin{array}{l}|{\displaystyle \frac{3}{2}}x+{\displaystyle \frac{1}{9}}|=0\\ |{\displaystyle \frac{5}{7}}y-{\displaystyle \frac{1}{2}}|=0\end{array}$

   => $\{\begin{array}{l}{\displaystyle \frac{3}{2}}x+{\displaystyle \frac{1}{9}}=0\\ {\displaystyle \frac{5}{7}}y-{\displaystyle \frac{1}{2}}=0\end{array}$

   => $\{\begin{array}{l}{\displaystyle \frac{3}{2}}x=-{\displaystyle \frac{1}{9}}\\ {\displaystyle \frac{5}{7}}y={\displaystyle \frac{1}{2}}\end{array}$

   => $\{\begin{array}{l}x=-{\displaystyle \frac{2}{27}}\\ y={\displaystyle \frac{7}{10}}\end{array}$

   Vậy (x;y) = ( -2/27 ; 7/10 )

   Trả lời
2. Giải đáp:

    

   Lời giải và giải thích chi tiết:

    b)|3/2x+1/9|+|5/7y-1/2|=0

   Vì |3/2x+1/9|>=0AAx

   |5/7y-1/2|>=0AAy

   =>|3/2x+1/9|+|5/7y-1/2|>=0AAx,y

   Vậy để |3/2x+1/9|+|5/7y-1/2|=0

   <=>{(|3/2x+1/9|=0),(|5/7y-1/2|=0):}

   <=>{(3/2x+1/9=0),(5/7y-1/2=0):}

   <=>{(3/2x=-1/9),(5/7y=1/2):}

   <=>{(x=-2/27),(y=7/10):}

   Vậy x=-2/27 và y=7/10.

   Trả lời