4x^2-23x=6
=>4x^2-23x-6=0
The rule to factor is to multiply 4 and -6 = -24 try a combination of this to get -23... which is in this case are -24 and 1
therefore re-write the equation as below:
4x^2 - 24x + x -6 = 0
4x(x-6) + 1(x-6) = 0
(x-6)(4x+1) = 0
=> x = 6
or 4x + 1 = 0
=> x = -1/4