\(1,-5x+3\ge0\)

\(\Leftrightarrow-5x\ge-3\)

\(\Leftrightarrow x\le\dfrac{3}{5}\)

\(2,3x-5>2x+1\)

\(\Leftrightarrow3x-2x>1+5\)

\(\Leftrightarrow x>6\)

\(3,8x+4\ge3x+19\)

\(\Leftrightarrow8x-3x\ge19-4\)

\(\Leftrightarrow5x\ge15\)

\(\Leftrightarrow x\ge3\)

\(4,3x-8\ge5x\)

\(\Leftrightarrow3x-5x\ge8\)

\(\Leftrightarrow-2x\ge8\)

\(\Leftrightarrow x\le-4\)

\(xy^2-3x+1\)

Thay \(x=1;y=2\) ta có:

\(\Rightarrow1.2^2-3.1+1\)

\(=1.4-3+1\)

\(=4-3+1\)

\(=2.\)

Cảm ơn nha:>

\(\dfrac{x-4}{x+3}=\dfrac{4}{5}\)

\(\Rightarrow5\left(x-4\right)=4\left(x+3\right)\)

\(\Rightarrow5x-20=4x+12\)

\(\Rightarrow5x-4x=12+32\)

\(\Rightarrow x=32\)

B