a)x2-8x-5x+40
=(x2-8x)-(5x-40)
=x.(x-8)-5.(x-8)
=(x-5).(x-8)
b)x2+5x-36
=x2-4x+9x-36
=(x2-4x)+(9x-36)
=x.(x-4)+9.(x-4)
=(x+9).(x-4)
c)2x2+3x-5
=2x2-2x+5x-5
=(2x2-2x)+(5x-5)
=2x.(x-1)+5.(x-1)
=(2x+5).(x-1)
d)6x2-7x+2
=6x2-3x-4x+2
=(6x2-3x)-(4x-2)
=3x.(2x-1)-2.(2x-1)
=(3x-2).(2x-1)
e)5x2-16x+3
=5x2-15x-x+3
=(5x2-15x)-(x-3)
=5x.(x-3)-(x-3)
=(5x-1).(x-3)