a) 4x-3√x-1=4x-4√x+√x-1=4√x(√x-1)+(√x+1)
=(4√x+1).(√x-1)
c) 12-2√27=9-2.3√3+3=32-2.3√3+(√3)2=(3-√3)2
d) 6x-√x-1=6x-3√x+2√x-1=3√x(2√x-1)+(2√x-1)
=(3√x+1).(2√x-1)
e) 11+2√30=6+2.√6.√5+5=(√6)2+2.√6.√5+(√5)2=(√6+√5)2
f) 10+2√21=7+2.√7.√3+3=(√7)2+2.√7.√3+(√3)2=(√7+√3)2