b) Nhận xét: (2x - 5)2012 \(\ge\) 0 với mọi x
(3y + 4)2014 \(\ge\) 0 với mọi x
=> (2x - 5)2012 + (3y + 4)2014 \(\ge\) 0 với mọi x
Mà (2x - 5)2012 + (3y + 4)2014 \(\le\) 0
=> (2x - 5)2012 + (3y + 4)2014 = 0
<=> (2x - 5)2012 = (3y + 4)2014 = 0
<=> 2x - 5 = 0 và 3y + 4 = 0
+) 2x - 5 = 0 => x = 5/2
+) 3y + 4 = 0 => y = -4/3
Vậy.............
a) Ta có : \(x\left(x-y\right)=\frac{3}{10}\Leftrightarrow\left(x-y\right)=\frac{3}{10.x}\) .
Ta lại có : \(y\left(x-y\right)=\frac{-3}{50}\Leftrightarrow\left(x-y\right)=\frac{-3}{50.y}\) .
\(\Rightarrow\left(x-y\right)=\frac{3}{10.x}=\frac{-3}{50.y}\Rightarrow3.50.y=-3.10.x\) .
\(\Rightarrow150.y=-30.x\Leftrightarrow\frac{x}{y}=\frac{150}{-30}=-5\).
\(\Rightarrow x-y=-5\) .
\(x.\left(-5\right)=\frac{3}{10}\Rightarrow x=-\frac{3}{50}\) .
\(y.\left(-5\right)=\frac{-3}{50}\Rightarrow y=\frac{3}{250}\).
b) \(Do:\) \(\left(2x-5\right)^{2012}\) là mũ chẵn \(\Rightarrow\left(2x-5\right)^{2012}\ge0\) .
Do : \(\left(3y+4\right)^{2014}\) cũng là mũ chẵn \(\Rightarrow\left(3y+4\right)^{2014}\ge0\) .
Để : \(\left(2x-5\right)^{2012}+\left(3y+4\right)^{2014}\le0\)
\(\Leftrightarrow\left(2x-5\right)=0\Leftrightarrow x=5:2=\frac{5}{2}\).
\(\Leftrightarrow3y+4=0\Leftrightarrow y=-4:3=\frac{-4}{3}\) .