a ) \(4x\left(5x+2\right)-\left(10x-3\right)\left(2x+7\right)=133\)
\(\Leftrightarrow20x^2+8x-\left(20x^2-6x+70x-21\right)=133\)
\(\Leftrightarrow20x^2+8x-20x^2+6x-70x+21=133\)
\(\Leftrightarrow-56x+21=133\)
\(\Leftrightarrow-56x=112\)
\(\Leftrightarrow x=-2\)
Vậy \(x=-2\)
b ) \(3\left(6x-5\right)\left(4x+1\right)-\left(8x+3\right)\left(9x-2\right)=203\)
\(\Leftrightarrow\left(18x-15\right)\left(4x+1\right)-\left(72x^2+27x-16x-6\right)=203\)
\(\Leftrightarrow72x^2-60x+18x-15-72x^2-27x+16x+6=203\)
\(\Leftrightarrow\left(72x^2-72x^2\right)+\left(18x+16x-60x-27x\right)-\left(15-6\right)=203\)
\(\Leftrightarrow-53x-9=203\)
\(\Leftrightarrow-53x=212\)
\(\Leftrightarrow x=-4\)
Vậy \(x=-4\)
