\(\left(5-6x\right)^2-64\)
\(=\left(5-6x-8\right)\left(5-6x+8\right)\)
\(=\left(-6x-3\right)\left(-6x+11\right)\)
\(=-3\left(2x+1\right)\left(-6x+11\right)\)
`(5-6x)^2 - 64`
`= (5 - 6x)^2 - 8^2`
`= [(5-6x)-8][(5-6x)+8]`
`= (5-6x-8)(5-6x+8)`
`= (-6x - 3)(-6x + 11)`
`= -3(2x + 1)(-6x+11)`