Gọi \(\dfrac{a}{b}\)=\(\dfrac{c}{d}\)=k\(\Rightarrow\)\(\left\{{}\begin{matrix}a=bk\\c=dk\end{matrix}\right.\)

Ta có:\(\dfrac{ab}{cd}\)=\(\dfrac{bk.b}{dk.d}\)=\(\dfrac{b^2.k}{d^2.k}\)=\(\dfrac{b^2}{d^2}\)(vì k khác 0) 1

\(\dfrac{\left(a-b\right)^2}{\left(c-d\right)^2}\)=\(\dfrac{\left(bk-b\right)^2}{\left(dk-d\right)^2}\)=\(\dfrac{\left[b.\left(k-1\right)\right]^2}{\left[d.\left(k-1\right)\right]^2}\)=\(\dfrac{b^2}{d^2}\)(vì k-1 khác 0) 2

Từ 1 và 2:

\(\Rightarrow\)\(\dfrac{\left(a-b\right)^2}{\left(c-d\right)^2}\)=\(\dfrac{ab}{cd}\)

Vậy \(\dfrac{\left(a-b\right)^2}{\left(c-d\right)^2}\)=\(\dfrac{ab}{cd}\)(điều cần chứng minh)

Gọi \(\dfrac{a}{b}\)=\(\dfrac{c}{d}\)=k\(\Rightarrow\)\(\left\{{}\begin{matrix}a=bk\\c=dk\end{matrix}\right.\)

Ta có:\(\dfrac{ab}{cd}\)=\(\dfrac{bk.b}{dk.d}\)=\(\dfrac{b^2.k}{d^2.k}\)=\(\dfrac{b^2}{d^2}\)=\(\left(\dfrac{b}{d}\right)^2\)(vì k khác 0) 1

\(\dfrac{\left(a+b\right)^2}{\left(c+d\right)^2}\)=\(\dfrac{\left(bk+b\right)^2}{\left(dk+d\right)^2}\)=\(\dfrac{\left[b.\left(k+1\right)\right]^2}{\left[d.\left(k+1\right)\right]^2}\)\(\left(\dfrac{b}{d}\right)^2\)=(vì k+1 khác 0) 2

Từ 1 và 2:

\(\Rightarrow\)\(\dfrac{ab}{cd}\)=\(\dfrac{\left(a+b\right)^2}{\left(c+d\right)^2}\)

Vậy \(\dfrac{ab}{cd}\)=\(\dfrac{\left(a+b\right)^2}{\left(c+d\right)^2}\)(điều cần chứng minh)

Tính giá trị của biểu thức:

4\(\dfrac{7}{9}\):\(\left(\dfrac{-5}{18}\right)\)+\(\dfrac{48}{9}\).(-3\(\dfrac{3}{5}\))

=\(\dfrac{43}{9}\).\(\dfrac{-18}{5}\)+\(\dfrac{48}{9}\).\(\dfrac{-12}{5}\)

=\(\dfrac{43.\left(-18\right)}{9.5}\)+\(\dfrac{48.\left(-12\right)}{9.5}\)

=\(\dfrac{43.\left(-2\right)}{1.5}\)+\(\dfrac{48.\left(-4\right)}{3.5}\)

=\(\dfrac{-86}{5}\)+\(\dfrac{-192}{15}\)

=\(\dfrac{-258}{15}\)+\(\dfrac{-192}{15}\)

=-30

Bạn có viết nhầm đầu bài ko.Mình ko kẻ đc hình.

Tìm x

a)\(\dfrac{x}{4}\)=\(\dfrac{16}{128}\)

\(\Rightarrow\)x.128=16.4

x.128=64

x=64:128

x=\(\dfrac{1}{2}\)

Vậy x=\(\dfrac{1}{2}\)

b)\(1\dfrac{5}{6}\)=\(\dfrac{-x}{5}\)

\(\dfrac{11}{6}\)=\(\dfrac{-x}{5}\)

-x:5=\(\dfrac{11}{6}\)

-x=\(\dfrac{11}{6}\).5

-x=\(\dfrac{55}{6}\)

\(\Rightarrow\)x=\(\dfrac{-55}{6}\)

Vậy x=\(\dfrac{-55}{6}\)

c)4,25:8 = -3,5:x

-3,5:x=\(\dfrac{17}{4}\)

x=-3,5:\(\dfrac{17}{4}\)

x=\(\dfrac{14}{17}\)

Vậy x=\(\dfrac{14}{17}\)

1.Trang received a letter from her aunt last week.

2.Eating too much candy is bad for you.

3.My school team took part in walking competition last year.

4.They always go to school on foot.

ta có : (x+2).(y-3)=-3=-1.3=-3.1

+/ 

x+2=-1=>x=-3

y-3=3=>y=6

+/

x+2=3=>x=1

y-3=-1=>x=2

vậy x=-3 thì y=6

x=1 thì y=2

Complete the advive for a healthy lifestyle,using more and less

1.Eat less sweet food.

vì số chia hết cho 5 có tận cùng là : 0;5 nên số 5 là bắt buộc

các số có tổng chia hết cho 9 là :

3+1+5

vậy các số lập được là :

315;135