Her

Từ đơn:lê-ki-ma,ầm ĩ,yên tĩnh,bồ kết,xà phòng.

Từ láy:san sát,chùa chiền,hân hạnh,mơ mộng,lóng ngóng.

D

Câu 1:

a)x²(5x³-x-6)=5x⁵-x³-6x²

b)(x²-2xy+y²).(x-y)=(x-y)².(x-y)=(x-y)³

Câu 2:

a)y²+2y+1=y²+2y+1²=(y+1)²

b)9x²+y²-6xy=(3x)²-6xy+y²=(3x-y)²

c)25a²+4b²+20ab=(5a)²+20ab+(2b)²=(5a+2b)²

d)x²-x+\(\dfrac{1}{4}\)=x²-x+(\(\dfrac{1}{2}\))²=(x-\(\dfrac{1}{2}\))²

Câu 4:

a)14x²y-21xy²+28x²y²=7xy(2x-3y+4xy)

b)27x³-\(\dfrac{1}{27}\)=27(x³-\(\dfrac{1}{729}\))

c)3x²-3xy-5x+5y=(3x²-3xy)-(5x-5y)=3x(x-y)-5(x-y)=(x-y)(3x-5)

d)x²-2xy+3x-6y=(x²-2xy)+(3x-6y)=x(x-2y)+3(x-2y)=(x-2y)(x+3)

(2x+3y)²=(2x)²+2.2x.3y+(3y)²=4x²+12xy+9y²

B

a)x³-1=x³-1³=(x-1).(x²+x.1+1²)=(x-1).(x²+x+1)

b)x³-8=x³-2³=(x-2).(x²+x.2+2²)=(x-2).(x²+2x+4)

c)x³-27=x³-3³=(x-3).(x²+x.3+3²)=(x-3).(x²+3x+9)

d)x³-64=x³-4³=(x-4).(x²+x.4+4²)=(x-4).(x²4x+16)

e)x³-125=x³-5³=(x-5).(x²+x.5+5²)=(x-5).(x²+5x+25)

f)(2x)³-1=(2x)³-1³=(2x-1).[(2x)²+2x.1+1²]=(2x-1).(4x²+2x+1)

g)1-27x³=1³-(3x)³=(1-3x).[1²+1.3x+(3x)²]=(1-3x).(1+3x+9x²)

h)(2x)³-(3y)³=(2x-3y).[(2x)²+2x.3y+(3y)²]=(2x-3y).(2x²+6xy+9y²)

i)x⁶-8y⁶=x⁶-2³y⁶=x⁶-(2y²)³=(x-2y²).[x²+x.2y²+(2y²)²]=(x-2y²).(x²+2xy²+4y⁴)

j)8(xy)³-125x³=(2xy)³-(5x)³=(2xy-5x).[(2xy)²+2xy.5x+(5x)²]=(2xy-5x).(4x²y²+10x²y+25x²)

k)1-27y³=1³-(3y)³=(1-3y).[1²+1.3y+(3y)²]=(1-3y).(1+3y+9y²)

l)8y³+x³y³=(2y)³+(xy)³=(2y-xy).[(2y)²+2y.xy+(xy)²]=(2y-xy).(4y²+2xy²+x²y²)

a)x³+1=x³+1³=(x+1).(x²-x.1+1²)=(x+1).(x²-x+1)

b)x³+27=x³+3³=(x+3).(x²-x.3+3²)=(x+3).(x²-3x+9)

c)x³+8=x³+2³=(x+2).(x²-x.2+2²)=(x+2).(x²-2x+4)

d)x³+y³=(x+y).(x²-x.y+y²)=(x+y).(x²-xy+y²)

e)(2x)³+y³=(2x+y).[(2x)²-2x.y+y²]=(2x+y).(4x²-2xy+y²)

f)x³+(3y)³=(x+3y).[x²-x.3y+(3y)²]=(x+3y).(x²-3xy+9y²)

g)(2x)³+(4y)³=(2x+4y).[(2x)²-2x.4y+(4y)²]=(2x+4y).(4x²-8xy+16y²)

h)8x³+1=(2x)³+1³=(2x+1).[(2x)²-2x.1+1²]=(2x+1).(4x²-2x+1)

i)27x³+8x³y³=(3x)³+(2xy)³=(3x+2xy).[(3x)²-3x.2xy+(2xy)²]=(3x+2xy).(9x²-6x²y+4x²y²)

j)125x³+1=(5x)³+1³=(5x+1).[(5x)²-5x.1+1²]=(5x+1).(25x²-5x+1)

k)x⁹+8=(x³)³+2³=(x³+2).[(x³)²-x³.2+2²]=(x³+2).(x⁶-2x³+4)

l)x⁶+y⁶=(x²)³+(y²)³=(x²+y²).[(x²)²-x².y²+(y²)²=(x²+y²).(x⁴-x²y²+y⁴)

Câu 12:D

Câu 13:B

D