4/1 x 13/15

= 52/15

52/15

mình có câu trl rồi nhé:

4 x 13/15 = 4 x 13/15 = 52/15 nhé!

29 because

30 but

\(A=\dfrac{\dfrac{\sqrt{2}}{2}\left(cosa-sina\right)+\dfrac{\sqrt{2}}{2}\left(cosa+sina\right)}{\dfrac{\sqrt{2}}{2}\left(cosa-sina\right)-\dfrac{\sqrt{2}}{2}\left(cosa+sina\right)}\)

\(=\dfrac{2cosa}{-2sina}=-cota\)

\(B=\dfrac{\sqrt{2}cosa-2.\dfrac{\sqrt{2}}{2}\left(cosa-sina\right)}{-\sqrt{2}sina+2.\dfrac{\sqrt{2}}{2}\left(cosa+sina\right)}\)

\(=\dfrac{\sqrt{2}sina}{\sqrt{2}cosa}=tana\)

a: góc AEH=góc ADH=góc DAE=90 độ

=>AEHD là hcn

b: XétΔAEH vuông tại E và ΔAHC vuông tại H có

góc EAH chung

=>ΔAEH đồng dạng với ΔAHC

c: ΔAHC vuông tại H có HE là đường cao

nên HE^2=AE*EC

\(A=\dfrac{1}{5}+\dfrac{1}{10}+\dfrac{1}{20}+\dfrac{1}{40}+\dfrac{1}{80}+\dfrac{1}{160}\\ A=\dfrac{35}{160}+\dfrac{16}{160}+\dfrac{8}{160}+\dfrac{4}{160}+\dfrac{2}{160}+\dfrac{1}{160}\\ A=\dfrac{66}{160}\\ A=\dfrac{33}{80}.\)

e cam on ah !

`1/5 + 1/10 + 1/20+1/40+1/80 + 1/160=A`

`<=> (32+16+8+4+2+1)/160=A`

`<=> 63/160=A`

76 Young people of different nationalities

77 There are ten expeditions every year

78 Each expedition lasts for ten weeks and takes 150 volunteers

79 Help scientists to do environmental research

80 It is English

76. Young people goes on expeditions.

77. There are ten expeditions every year.

78. Each expedition last for ten week.

79. Volunteer help scientists to do environmental research.

80. We must know speak English to become a volunteer.

\(\left(4xy^2-6x^2y+8x^2y^2\right):\left(2xy\right)-3y\\ =\left(4xy^2:2xy-6x^2y:2xy+8x^2y^2:2xy\right)-3y\\ =2y-3x+4xy-3y=-y-3x+4xy\)