a) điều kiện \(x\ne4\)
b) \(\dfrac{7x^2-29x+4}{x^2-16}\Leftrightarrow\dfrac{7x^2-28x-x+4}{\left(x-4\right)\left(x+4\right)}\Leftrightarrow\dfrac{7x\left(x-4\right)-\left(x-4\right)}{\left(x-4\right)\left(x+4\right)}\)
\(\Leftrightarrow\dfrac{\left(7x-1\right)\left(x-4\right)}{\left(x-4\right)\left(x+4\right)}\Leftrightarrow\dfrac{7x-1}{x+4}\)