d:
Sửa đề: \(4x\left(x-5\right)-7\left(x-4\right)^2+3x^2=12\)
\(\Leftrightarrow4x^2-20x-7\left(x-4\right)^2+3x^2=12\)
\(\Leftrightarrow7x^2-20x-7\left(x^2-8x+16\right)=12\)
\(\Leftrightarrow7x^2-20x-7x^2+56x-112=12\)
=>36x=124
hay x=31/9
e: \(\Leftrightarrow15x-3-x^2+2x+x^2-13x=7\)
=>4x-3=7
hay x=5/2