a, 53.25 - 25.12 + 75.53

= ( 53.25 + 75.53) - 25.12

= 53.(25+75) - 25.12

= 53.100 - 300

= 5300 -300

= 5000

b, 260:/5+7.(72:2^3 - 6)/ - 3^2

= 260:/5+7.(72:8-6)/ - 9

= 260:/5+7.(9-6)/ - 9

= 260:/5+7.3/ - 9

= 260:/5+21/-9

= 260:26-9

= 10 - 9

= 1

a, x:3;x:5 va x:7,va x nho nhat 

BCNN(3;5;7) la: 3 = 1.3; 5 = 1.5; 7 = 1.7. Vay BCNN (3;5;7) la 1.3.5.7=105

b, Goi co the chia duoc phan qua la x (x e n*). Khi do x la UCLN(24;36;60)

Ta co: 24=2^3.3;36=2^2.3^2;60=2^2.3.5

Vay UCLN(24;36;60) la 2^2.3=4.3=12

Vay moi tui co 2 goi banh,3 hop sua,5 khan len

Goi DT ao cu la x. Thi DT ao moi la x+600 ma DT ao moi gap 4 lan ao cu. Nen Dt ao cu la 200 m2

vay DT ao moi la : 200 + 600 = 800 m2. Dt hinh vuong la: 800 : 2 = 400 m2. Mot canh hinh vuong la 20 m

Suy ra chieu rong ao moi la 20m . Chieu dai cua ao moi la : 20.2 = 40 m. CHu vi ao moi la: (20+40).2=120m

Can dung so chiec coc la : (120-2):1+1 = 119 coc

TH1: x = 1;y = -3 , x+y= 1+(-3) =-2(loai)

TH2: x = -3;y = 1,x+y=(-3)+1 =-2(loai)

TH3: x = -1;y = 3,x+y=(-1)+3 =2

TH4: x = 3;y = -1,x+y=3+(-1) =2

Vay x;y du dieu kien la -1;3 va 3;-1

Co the thay dau * de so 2* la so nguyen to

Vay so * la 3 va 9

(-4)^2.(-3)-/(-93)+(-11+8)^3/

= (-4)^2.(-3)-/(-93)+(-3)^3/

= 16.(-3) - /(-93)+(-27)/

= -48 - (-120)

= 72

-4<(bang) x<(bang) 5

Cac so -4<(bang)x<(bang) 5 la : -4;-3;-2;-1;0;1;2;3;4;5

Tinh tong: (-4) +(-3)+(-2)+(-1)+0+1+2+3+4+5

= (-4)+4+(-3)+3+(-2)+2+(-1)+1+5

= 0+0+0+0+5

= 5

Bai 7:

a, Goi tong so nguoi cua doi do la x( X E N*/150< (bang) x <(bang) 200. Khi do x la BCNN ( 4,5,6). Ta co:

4= 2^2, 5=1.5,6=2.3.Vay BCNN(4;5;6) la 60

B(60)=(0;60;120;180;240;300;360;...) ma 150< (bang) x < (bang) nen x se la 180 nguoi .

b,Hien tai no o vi tri nao so voi mat nuoc la : (-165) + 285 = 120 ( cm)

D/S: a;180 nguoi,b;120 cm

A=2011+2012+2013+2014+2015+2016+2017+2018+2019

A= (2011+2019) +(2012+2018) +(2013+2017)+(2014+2016) + 2015

A= 4030 + 4030 + 4030 + 4030 + 2015

A= 16120 + 2015

A= 18135

Chu vi can phong hinh chu nhat la: (10+6).2 = 32 (m)

Vi chu vi hinh vuong bang chu vi hinh chu nhat nen chu vi hinh vuong la 32m

Canh cua can phong hinh vuong la: 32:4=8(m)

Dien tich can phong hinh vuong la:8.8=64(m2)

D/S: 64 m2