11)
a)(x+2y)2
=x2 + 2*x*2y+(2y)2
=x2 + 4xy + 4y2
b)(x-3y)(x+3y)
= x*x+x*3y-3y*x-3y*3y
=x2+3xy-3xy-3y23-
=x2-(3y)2
c)(5-x)222
=52-2*5*x+x2
=25-10x+x2
12)
a)(x-1)2
=x2-2*x*1+12
=x2-2x+1
b)(3-y)2
=32-2*3*y+y2
=9-6y+y2
c)(x-1/2)2
=x2-2*x*1/2+(1/2)2
=x2-1x2+1/4
13 )
a)x2+6x+9
=x2+2*3*x+32
=x2+6x+9
b)x2+x+1/4
=x2+2*x*1/2+(1/2)2
=(x+1/2)2
c)2xy2+x2y4+1
=(xy2)2+2xy2+1
=(xy2+1)2
14)
a)(x+y)2+(x-y)2
=x2+2xy+y2+x2-2xy+y2
=2x2+2y2
b)2(x-y)(x+y)+(x+y)2+(x-y)2
=(x-y)2+2(x-y)(x+y)+(x+y)2
=(x-y+x+y)2
=(x+x)2
c)(x-y+z)2+(z-y)2+2(x-y+z)(y-z)
=(x-y+z)2+2(x-y+z)(y-z)+ +(z-y)2
=( x-y+z+ z-y)2
16)
a)x2-y2 tại x=87 và y = 13
=872-132
=(87+13)(87-13)
=100*74
=7400
b)x3-3x2+3x-1 tại x=101
=x3-3x2*1+3x*12
=(x-1)3
=(101-1)3
=1003
=1000000
c)x3+9x2+27x+27 tại x= 97
=x3+3*x2*3+3*x*33 +
33
=(x+3)3
=(97+3)3
=1003
=1000000
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