\(f)18,36^2-2.18.36.8,36+8,36^2=(18,36-8,36)^2\) 

g tự làm nha 

1 a) \(x^2-20x+100=x^2-2.x.10+10^2=(x+10)^2\) 

b) \(9x^2-12xy+4y^2=(3x)^2-2.3.x.y +(2y)^2=(3x-2y)^2\) 

d) \(x^3-36x^2+108x-216=x^3-2.x^2.6+2.x.6^2-6^3=(x-6)^3\) 

\(c)x^3+15x^2+75x+125=(x+3)^3\) 

2 d) \(58.42=(50-8)(50+8)=50^2-42^2=2500-1764=736\) 

e)\(36.44=(40-4)(40+4)=40^2-36^2=1600-1296=304\) 

a) \(51^2=(50 + 1)=50^2+2.50.1+1^2=2500+100+1=2601\) 

b)\(201^2=(200+1)^2=200^2+2.200.1+1^2=40000+400+1=40401\) 

c) \(199^2=(200-1)^2=200^2-2.200.1+1^2=40000-400+1=39601\) 

\(2x - 138 = 2^3 .2^2<=>2x-138=8.4\) 

\(<=>2x-138=32\) 

\(<=>2x=138+32\) 

\(<=>2x=170\) 

\(<=>x=170:2\) 

\(<=>x =85\)

1d

2c

3b

4a

5b

6d

7a 

5x²y - 30xy² + 45y³

= 5y(x² - 6xy + 9y)

 a) 85. 12,7 + 5,3. 127

= 12,7 . ( 85 + 5.3 )

= 12,7 . (85 + 15)

= 12,7 . 100

= 1270

b) 52. 143 – 52. 39 – 8. 26

= 52.143 - 52.39 - 4.2.26

= 52.143 - 52.39 - 4.52  

= 52.( 143 -39 - 4 )

= 52 . 100

= 5200

trung bình mỗi quyển sách là  

(450 + 620 +766) : 3 = 612 quyển sách

16834838 = 10000000 + 6000000 + 800000 + 30000 + 4000 + 800 + 30 + 8