Ta có: 

\(\widehat{A}+\widehat{B}+\widehat{C}=180^o\)

\(\Rightarrow90^o+\widehat{B}+40^o=50^o\)

Theo giả thiết:

\(AD\) là phân giác của \(\widehat{A}\)

\(\Rightarrow\widehat{BAD}=45^o\)

Ta có: 

\(\widehat{BAH}+\widehat{AHB}+\widehat{ABH}=180^o\)

\(\Rightarrow90^o+\widehat{AHB}+50^o=180^o\)

\(\Rightarrow\widehat{AHB}=40^o\)

Ta có:

\(\widehat{BAH}+\widehat{HAD}=45^o\)

\(\Rightarrow40^o+\widehat{HAD}=45^o\)

\(\Rightarrow\widehat{HAD}=5^o\).

1.

(x-2,5).2-3,5=4

(x-2,5).2      =4+3,5

(x-2,5).2      =7,5

x-2,5           =7,5:2

x-2,5           =3,75

x                 =3,75+2,5

x                 =6,25

Vậy x = 6,25

2.

(2x+4,2)-3,6=5

2x+4,2        =5+3,6

2x+4,2        =8,6

2x               =8,6-4,2

2x               =4,4

x                 =4,4:2

x                 =2,2

vậy x = 2,2

99:10=9(dư 9)

Đ/S 99

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

\(\dfrac{3}{4}x+\dfrac{4}{5}x=\dfrac{4}{5}+3\)

\(\dfrac{31x}{20}=\dfrac{19}{5}\)

\(x\) = \(\dfrac{19}{5}:\dfrac{31}{20}\)

\(x\) = 76/31

Bảng số La Mã không có số 0

|x+1|=\(\dfrac{8}{3}\)-\(\dfrac{2}{3}\)

|x+1|=2

TH1: x+1=2                   TH2: x+1=-2

        x=2-1                             x=-2-1

        x=1                                x=-3

vậy x={1;-3}

\(\dfrac{8}{3}-\left|x+1\right|=\dfrac{2}{3}\)

\(\left|x+1\right|=\dfrac{8}{3}-\dfrac{2}{3}\)

\(\left|x+1\right|=2\)

\(x+1=2\)  hoặc \(x+1=-2\)

TH1 : \(x+1=2\)

\(x=2-1\)

\(x=1\)

TH2 : \(x+1=-2\)

\(x=-2-1\)

\(x=-3\)

Vậy x = 1 hoặc x = -3

Bằng 77/72 nhé bạn

Trả lời:

\(\sqrt{\dfrac{49}{100}}=\sqrt{\dfrac{7}{10}}\)

\(\sqrt{\dfrac{49}{100}}=\dfrac{7}{10}\)

\(\dfrac{2}{5}+\dfrac{3}{5}x=\left(\dfrac{1}{5}\right)^7\times\left(\dfrac{1}{5}\right)^5\)

\(\Rightarrow\dfrac{2}{5}+\dfrac{3}{5}x=\left(\dfrac{1}{5}\right)^{12}\)

\(\Rightarrow\dfrac{3}{5}x=-0,3999999959\)

\(\Rightarrow x=-0,9999999959\).

     \(\dfrac{6^8.4^3}{9^4.12^6}\)

=   \(\dfrac{2^8.3^8.2^6}{3^8.3^6.2^{12}}\)

= 4/729