`14.`
`a)81²`
`=(80+1)²`
`=80²+2.80.1+1²`
`=6400+160+1`
`=6561`
`b)102²`
`=(100+2)²`
`=100²+2.100.2+2²`
`=10` `000+400+4`
`=10` `404`
`c)97.103`
`=(100-3)(100+3)`
`=100²-3²`
`=10` `000-9`
`=9` `991`
`d)249.351`
`=(300-51)(300+51)`
`=300²-51²`
`=90` `000-2` `601`
`=87` `399`
`15.`
`a)A=(5x+5)²+10(x-3)(1+x)+x²-6x+9`
`=[5(x+1)]²+2.5(x+1).(x-3)+(x-3)²`
`=[5(x+1)+x-3]²`
`=(5x+5+x-3)²`
`=(6x+2)²`
`b)B=[(x-1)²]/4+x²-1+(x+1)²`
`=((x-1)/2)^2+(x-1)(x+1)+(x+1)²`
`=((x-1)/2)^2+2.(x-1)/2 .(x+1)+(x+1)²`
`=((x-1)/2+x+1)^2`
`=((x-1+2x+2)/2)^2`
`=((3x+1)/2)^2`
