a) Ta có: \(5x\left(x-9\right)-x+9\)
\(=5x\left(x-9\right)-\left(x-9\right)\)
\(=\left(x-9\right)\left(5x-1\right)\)
b) Ta có: \(6x^2+7x-3\)
\(=6x^2+9x-2x-3\)
\(=3x\left(2x-3\right)-\left(2x-3\right)\)
\(=\left(2x-3\right)\left(3x-1\right)\)
d) Ta có: \(x^2-10xy+25y^2\)
\(=x^2-2\cdot x\cdot5y+\left(5y\right)^2\)
\(=\left(x-5y\right)^2\)