\(\dfrac{2}{67}-\left(\dfrac{3}{7}+\dfrac{2}{67}\right)\\ =\dfrac{2}{67}-\dfrac{215}{469}\\ =\dfrac{-3}{7}\)

\(\dfrac{3}{4}.\dfrac{5}{2}+\dfrac{5}{4}.\dfrac{5}{2}\\ =\left(\dfrac{3}{4}+\dfrac{5}{4}\right).\dfrac{5}{2}\\ =2.\dfrac{5}{2}\\ =\dfrac{5}{1}\)

Bài 2:

a: \(\Leftrightarrow x:\dfrac{4}{5}=\dfrac{-4}{6}+\dfrac{3}{6}=\dfrac{-1}{6}\)

=>x=-1/6*4/5=-4/30=-2/15

b: =>1/6x=5/6-7/12+1/3=10/12-7/12+4/12=7/12

=>x=7/2

c: =(47/11-3x)*11/5=-21/5

=>47/11-3x=-21/5:11/5=-21/11

=>3x=68/11

=>x=68/33

\(\frac{3}{5}.\left(\frac{5}{3}-\frac{2}{7}\right)-\left(\frac{7}{3}-\frac{3}{7}\right).\frac{3}{5}\)

\(=\frac{3}{5}.\text{[}\left(\frac{5}{3}-\frac{2}{7}\right)-\left(\frac{7}{3}-\frac{3}{7}\right)\text{]}\)

\(=\frac{3}{5}.\text{[}\frac{5}{3}-\frac{2}{7}-\frac{7}{3}+\frac{3}{7}\text{]}\)

\(=\frac{3}{5}.\text{[}\left(\frac{5}{3}-\frac{7}{3}\right)-\left(\frac{2}{7}-\frac{3}{7}\right)\text{]}\)

\(=\frac{3}{5}.\text{[}\frac{-2}{3}-\frac{-1}{7}\text{]}\)

\(=\frac{3}{5}.\left(\frac{-2}{3}+\frac{1}{7}\right)\)

\(=\frac{3}{5}.\left(\frac{-14}{21}+\frac{3}{21}\right)\)

\(=\frac{3}{5}.\frac{-11}{21}\)

\(=\frac{3.\left(-11\right)}{5.21}\)

\(=\frac{-11}{5.7}=\frac{-11}{35}\)

Chúc bạn học tốt

a, - \(\dfrac{1}{3}\).\(xy\).(3\(x^3\).y² - 6\(x^2\) + y²)

= - \(x^4\).y³ + 2\(x^3\).y - \(\dfrac{1}{3}\).\(xy^3\)

b, (2\(x\) -3).(4\(x\)² + 6\(x\) + 9)

 = (2\(x\))³ - 3³

= 8\(x^3\) - 27 

Bài 3:

a: \(P=x\left(x^2-y\right)+y\left(x-y^2\right)\)

\(=x^3-xy+xy-y^3\)

\(=x^3-y^3\)

Thay \(x=-\frac12;y=-\frac12\) vào P, ta được:

\(P=\left(-\frac12\right)^3-\left(-\frac12\right)^3=\left(-\frac18\right)-\left(-\frac18\right)=-\frac18+\frac18=0\)

b: \(Q=x^2\left(y^3-xy^2\right)+x^2y^2\left(x-y+1\right)\)

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

Thay x=-10; y=-10 vào Q, ta được:

\(Q=\left(-10\right)^2\cdot\left(-10\right)^2=100\cdot100=10000\)

c: \(A=x^3+2xy-2x^3+2y^3+2x^3-y^3\)

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

\(=x^3+2xy+y^3\)

Thay x=2; y=-3 vào A, ta được:

\(A=2^3+2\cdot2\cdot\left(-3\right)+\left(-3\right)^3\)

=8-12-27

=-4-27

=-31

d:

x=1; y=-1

=>\(xy=1\cdot\left(-1\right)=-1\)

\(B=xy+x^2y^2-x^4y^4+x^6y^6-x^8y^8\)

\(=\left(xy\right)+\left(xy\right)^2-\left(xy\right)^4+\left(xy\right)^6-\left(xy\right)^8\)

\(=\left(-1\right)+\left(-1\right)^2-\left(-1\right)^4+\left(-1\right)^6-\left(-1\right)^8\)

=-1+1-1+1-1

=-1

e: x=-1; y=1

=>xy=-1

\(C=xy+x^2y^2+x^3y^3+\cdots+x^{10}y^{10}\)

\(=xy+\left(xy\right)^2+\left(xy\right)^3+\cdots+\left(xy\right)^{10}\)

\(=\left(-1\right)+\left(-1\right)^2+\left(-1\right)^3+\cdots+\left(-1\right)^{10}\)

=-1+1+(-1)+1+...+(-1)+1

=0

f: \(M=2x^2\left(x^2-5\right)+x\left(-2x^3+4x\right)+x^2\left(x+6\right)\)

\(=2x^4-10x^2-2x^4+4x^2+x^3+6x^2\)

\(=x^3\)

Khi x=-4 thì \(M=\left(-4\right)^3=-64\)

g: \(N=x^3\left(y+1\right)-xy\left(x^2-2x+1\right)-x\left(x^2+2xy-3y\right)\)

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

=2xy

Thay x=8; y=-5 vào N, ta được:

\(N=2\cdot8\cdot\left(-5\right)=-80\)

Bài 1:

d: \(x^2+2xy-3\cdot\left(-xy\right)\)

\(=x^2+2xy+3xy=x^2+5xy\)

e: \(\frac12x^2y\left(2x^3-\frac25xy^2-1\right)\)

\(=\frac12x^2y\cdot2x^3-\frac12x^2y\cdot\frac25xy^2-\frac12x^2y\)

\(=x^5y-\frac15x^3y^3-\frac12x^2y\)

f: \(\left(-xy^2\right)^2\left(x^2-2x+1\right)\)

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

\(=x^2y^4\cdot x^2-x^2y^4\cdot2x+x^2y^4\)

\(=x^4y^4-2x^3y^4+x^2y^4\)

g: (2xy+3)(x-2y)

\(=2xy\cdot x-2xy\cdot2y+3\cdot x-3\cdot2y\)

\(=2x^2y-4xy^2+3x-6y\)

h: \(\left(xy+2y\right)\left(x^2y-2xy+4\right)\)

\(=x^3y^2-2x^2y^2+4xy+2x^2y^2-4xy^2+8y\)

\(=x^3y^2+4xy-4xy^2+8y\)

i: \(4\left(x^2-\frac12y\right)\left(x^2+\frac12y\right)\)

\(=4\left(x^4-\frac14y^2\right)\)

\(=4\cdot x^4-4\cdot\frac14y^2=4x^4-y^2\)

k: \(2x^2\left(1-3x+2x^2\right)\)

\(=2x^2\cdot1-2x^2\cdot3x+2x^2\cdot2x^2\)

\(=2x^2-6x^3+4x^4\)

l: \(\left(2x^2-3x+4\right)\left(-\frac12x\right)\)

\(=-\frac12x\cdot2x^2+3x\cdot\frac12x-4\cdot\frac12x=-x^3+\frac32x^2-2x\)

m: \(\frac12xy\left(-x^3+2xy-4y^2\right)\)

\(=-\frac12xy\cdot x^3+\frac12xy\cdot2xy-\frac12xy\cdot4y^2\)

\(=-\frac12x^4y+x^2y^2-2xy^3\)

n: \(\frac12x^2y\left(2x^3-\frac25xy^2-1\right)\)

\(=\frac12x^2y\cdot2x^3-\frac12x^2y\cdot\frac25xy^2-\frac12x^2y\)

\(=x^5y-\frac15x^3y^3-\frac12x^2y\)

b)1024(5)-132(5)=892(5)

c)214(5).32(5)=6848(5)

d)211(5):13(5)=17(5)

2,1001(2):11(2)=91(2)

hehe làm bừa sai xin lỗivì tui ko hiểu

Câu 1 cứ bình phương lên mà viết thôi

Câu 2:

(1 + 3 + 5 +...+ 97 + 99).(45.3) - (5.9.2 - 15.3) 

= {50.[2.1 + (50 - 1).2]} : 2.(45.3) - (5.9.2 - 15.3)

= 2500.135 - 45 

= 337455

\(\text{a.545.65 + 15.545 - 80.445}.\)

\(=545\left(65+15\right)-80.445=545.80-80.445=80\left(545-445\right)=80.100=8000.\)

\(b.480:\left[75+\left(7^2-8.3\right)\right].\)

\(=480:\left[75+\left(49-24\right)\right]=480:\left(75+25\right)=480:100=4,8.\)

\(\text{c.36.13 + 64.37 + 9.4.87 + 64.9.7 }.\)

\(=\text{36.13 + 64.37 + 36.87 + 64.63 }\)\(=36\left(13+87\right)+64\left(37+63\right)=36.100+64.100=100\left(36+64\right)=100.100=10000.\)

HOC24

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'Giang' ĐZ ơi bạn nhập bài muốn hỏi vào đây

Nguyễn Thanh Thảo

Nguyễn Thanh Thảo

14 tháng 12 2021 lúc 16:41

Bài 1: Thực hiện phép tính: Nhanh đị ạ mình cần gấp

a) 545.65 + 15.545 - 80.445

b) 480: [ 75 + ( 72 - 8.3 )

c) 36.13 + 64.37 + 9.4.87 + 64.9.7          

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Viết câu trả lời giúp Nguyễn Thanh Thảo

Thanh Hoàng Thanh

Thanh Hoàng Thanh

14 tháng 12 2021 lúc 16:49

a.545.65 + 15.545 - 80.445

.

=

545

(

65

+

15

)

−

80.445

=

545.80

−

80.445

=

80

(

545

−

445

)

=

80.100

=

8000.

b

.480

:

[

75

+

(

7

2

−

8.3

)

]

.

=

480

:

[

75

+

(

49

−

24

)

]

=

480

:

(

75

+

25

)

=

480

:

100

=

4

,

8.

c.36.13 + 64.37 + 9.4.87 + 64.9.7 

.

=

36.13 + 64.37 + 36.87 + 64.63 

=

36

(

13

+

87

)

+

64

(

37

+

63

)

=

36.100

+

64.100

=

100

(

36

+

64

)

=

100.100

=

10000.

giúp em  bài với ạ,em cảm ơn, em đang vội ạ

\(a,=-15x^3+10x^4+20x^2\\ b,=2x^3+2x^2+4x-x^2-x-2=2x^3+x^2+3x-2\)