\(a,\left(12x-5\right)\left(4x-1\right)+\left(3x-7\right)\left(1-16x\right)=81\\ \Leftrightarrow48x^2-20x-12x+5-3x-48x^2-7+112x-81=0\\ \Leftrightarrow77x=83\\ \Leftrightarrow x=\dfrac{83}{77}\)
\(b,\left(x-4\right)\left(x-1\right)=\left(x-2\right)\left(x-3\right)\\ \Leftrightarrow x^2-4x-x+4=x^2-2x-3x+6\\ \Leftrightarrow x^2-x^2-4x-x+2x+3x=6-4\\ \Leftrightarrow0x=2\left(vô.lí\right)\)
Vậy không có x thoả mãn
\(c,\left(3x-4\right)\left(2x+1\right)-\left(6x+5\right)\left(x-3\right)=3\\ \Leftrightarrow6x^2-8x+3x-4-6x^2-5x+18x+15=0\\ \Leftrightarrow6x^2-6x^2-8x+3x-5x+18x=3+4-15\\ \Leftrightarrow8x=-8\\ \Leftrightarrow x=-1\)
