Bài 13:

a) \(501^2\)

\(=\left(500+1\right)^2\)

\(=500^2+2\cdot500\cdot1+1^2\)

\(=250000+1000+1\)

\(=251001\)

b) \(88^2+24\cdot88+12^2\)

\(=88^2+2\cdot12\cdot88+12^2\)

\(=\left(88+12\right)^2\)

\(=100^2\)

\(=10000\)

c) \(52\cdot48\)

\(=\left(50+2\right)\left(50-2\right)\)

\(=50^2-2^2\)

\(=2500-4\)

\(=2496\)

Bài 14:

a) \(P=\left(2x-1\right)\left(4x^2+2x+1\right)+\left(x+1\right)\left(x^2-x+1\right)\)

\(P=\left(2x\right)^3-1+x^3+1\)

\(P=8x^3+x^3\)

\(P=9x^3\)

b) \(Q=\left(x-y\right)\left(x^2+xy+y^2\right)-\left(x+y\right)\left(x^2-xy+y^2\right)+2y^3\)

\(Q=x^3-y^3-x^3-y^3+2y^3\)

\(Q=-2y^3+2y^3\)

\(Q=0\)

Bài `14`

`a. P = ( 2x - 1 ) ( 4x^2 + 2x + 1 ) + ( x + 1 ) ( x^2 -x+1)`

`=(2x)^3-1^3 + x^3+1^3`

`=8x^3-1+x^3+1`

`= 9x^3`

__

`b, Q = ( x - y ) ( x^2 + xy + y^2 ) - ( x + y ) ( x^2 - xy + y^2)+2y^3`

`=x^3-y^3 -(x^3+y^3)+2y^3`

`=x^3-y^3 -x^3-y^3+2y^3`

`= 0`

= 29540 : 29540

= 1

nhớ k cho mik vs nha Hải Yến

 ( 124 x 237 + 152 ) : ( 870 + 235 x 122) 
=[124 x (235+2) + 152 ] : [870 + 235 x (124-2)] 
=[124 x 235+124x2 + 152 ] : [870 + 235 x124 - 235x2] 
=[124 x 235+248 + 152 ] : [870 + 235 x 124 - 470] 
=[124 x 235+ 400 ] : [870 - 470 + 235 x 124 ] 
=[124 x 235+ 400 ] : [400 + 235 x 124 ] 
=1

( 124 x 237 + 152 ) : ( 870 + 235 x 122 )

= ( 29388 + 152 ) : ( 870 + 28670 )

= 29540 : 29540 

= 1

1700:9/8

1700:9/8

a/ 9,532;  b/ 26,851 ;     c/  64,6618    ;      d/ 24,5

a) \(136+326+64\)

\(=\left(136+64\right)+326\)

\(=200+326\)

\(=526\)

b) \(69+\left(31+57\right)\)

\(=\left(69+31\right)+57\)

\(=100+57\)

\(=157\)

c) \(755+321+145+179\)

\(=\left(755+145\right)+\left(321+179\right)\)

\(=900+500\)

\(=1400\)

d) \(17+123+378+583+122\)

\(=\left(17+583\right)+\left(378+122\right)+123\)

\(=600+500+123\)

\(=1100+123\)

\(=1223\)

=(112+128)+(114+126)+(116+124)+(118+122)+120

=240+240+240+240+120

= 120+120+120+120+120+120+120+120+120

= 120 x 9 

= 1080

tich nha ban oi , thanks

=(112+118)+(114+126)+(118+122)+120+116

=230+240+240+120+116

=470+360+116

=830+116

=946

112+114+116+118+120+122+126+128

=(112+128)+(114+126)+(118+122)+120+116

=240+240+240+120+116

=240x3+120+116

=720+120+116

=840+116

=956

Bài 1 : ( 200 + 800 ) + ( 155 + 845 ) = 1000 + 1000 = 2000

Bài 2 : 122 x 23 = 2806

1: 200+ 155+ 845+ 800

=(200+800)+(845+155)

=1000+1000

=2000

2: 122x23=2806

tk nha

Bài 1 : 2000

Bài 2 : 2806

= (31.4.237 + 4.38) : (435.2 + 2.235.61)

= [4.(31.237 + 38)] : [2.(435 + 61.235)]

= (4.7385) : (2.14770)

= 29540 : 29540

= 1