c) \(\left(3x-1\right).\left(2x+7\right)-\left(x+1\right).\left(6x-5\right)=\left(x+2\right)-\left(x-5\right)\)
\(\Leftrightarrow6x^2+21x-2x-7-\left(6x^2-5x+6x-5\right)=x+2-x+5\)
\(\Leftrightarrow18x-2-7=0\)
\(\Rightarrow x=\dfrac{9}{18}=\dfrac{1}{2}\)
b) \(2.\left(3x-1\right).\left(2x+5\right)-6.\left(2x-1\right).\left(x+2\right)=1\)
\(\Leftrightarrow\left(6x-2\right).\left(2x+5\right)-\left(12x-6\right).\left(x+2\right)=1\)
\(\Leftrightarrow12x^2+30x-4x-10-\left(12x^2+24x-6x-12\right)=1\)
\(\Leftrightarrow12x^2+26x-10-12x^2-18x +12=1\)
\(\Leftrightarrow8x+2=1\)
\(\Rightarrow x=\dfrac{-1}{8}\)
a) \(x.\left(x+1\right).\left(x+6\right)-x^3=5x\)
\(\Leftrightarrow\left(x^2+x\right).\left(x+6\right)-x^3=5x\)
\(\Leftrightarrow x^3+6x^2+x^2+6x-x^3-5x=0\)
\(\Leftrightarrow7x^2+x=0\)
\(\Leftrightarrow x.\left(7x+1\right)=0\)
\(\Rightarrow x=0\) hoặc \(x=\dfrac{-1}{7}\)
