tìm x,y biết |x-y|+|y+9/25|=0

Do  $\left \{ {{|x - y| ≥ 0 } \atop {|y + \frac{9}{25} | ≥ 0}} \right.$

Mà: |x - y| + |y + $\frac{9}{25}$| = 0

⇒  $\left \{ {{|x - y| = 0 } \atop {|y + \frac{9}{25} | = 0}} \right.$

⇒  $\left \{ {{x - y = 0 } \atop {y + \frac{9}{25}  = 0}} \right.$

⇒  $\left \{ {{x - \frac{-9}{25} = 0 } \atop {y = \frac{-9}{25} }} \right.$

⇒  $\left \{ {{x + \frac{9}{25} = 0 } \atop {y = \frac{-9}{25} }} \right.$

⇒  $\left \{ {{x = \frac{-9}{25}  } \atop {y = \frac{-9}{25} }} \right.$

Vậy x = y = $\frac{-9}{25}$