(x - a)(x - b)=x2 - (a + b)x + ab
(4x - 5)(4x -1)
a=5, b= 1,x=4x
[1 Mark]
(4x - 5)(4x - 1)= (4x)2 - [5 + 1](4x) + (-5) (-1)
(4x - 5)(4x - 1)= 16x2 - 24x + 5
[1 Mark]