a: \(\sqrt{5+2\sqrt{6}}=\sqrt{3}+\sqrt{2}\)

b: \(\sqrt{12+2\sqrt{35}}-\sqrt{12-2\sqrt{35}}=\sqrt{7}+\sqrt{5}-\sqrt{7}+\sqrt{5}=2\sqrt{5}\)

c: \(\sqrt{16+6\sqrt{7}}=4+\sqrt{7}\)

d: \(\sqrt{31-12\sqrt{3}}=3\sqrt{3}-2\)

e: \(\sqrt{27+10\sqrt{2}}=5+\sqrt{2}\)

f: \(\sqrt{14+6\sqrt{5}}=3+\sqrt{5}\)

a)\(\frac{7}{12}.\frac{6}{11}+\frac{7}{12}.\frac{5}{11}-2\frac{7}{12}\)

\(=\frac{7}{12}.\left(\frac{6}{11}+\frac{5}{11}\right)-\frac{31}{12}\)

\(=\frac{7}{12}-\frac{31}{12}\)

\(=-2\)

b)\(\frac{-5}{9}.\frac{-6}{13}+\frac{5}{-9}.\frac{-5}{13}-\frac{5}{9}\)

\(=\frac{5}{9}.\left(\frac{6}{13}+\frac{5}{13}-1\right)\)

\(=\frac{5}{9}.\left(\frac{11}{13}-\frac{13}{13}\right)\)

\(=\frac{5}{9}.\frac{-2}{13}\)

\(=-\frac{10}{117}\)

c)\(0,8.\frac{-15}{14}-\frac{4}{5}.\frac{13}{14}-1\frac{2}{5}\)

\(=\frac{4}{5}.\frac{-15}{14}-\frac{4}{5}.\frac{13}{14}-\frac{7}{5}\)

\(=\frac{4}{5}.\left(-\frac{15}{14}-\frac{13}{14}\right)-\frac{7}{5}\)

\(=\frac{4}{5}.\left(-2\right)-\frac{7}{5}\)

\(=\frac{-8}{5}-\frac{7}{5}\)

\(=-3\)

d)\(-75\%.\frac{6}{7}+5\%.\frac{6}{7}+\frac{7}{10}.1\frac{1}{7}\)

\(=\frac{-15}{20}.\frac{6}{7}+\frac{1}{20}.\frac{6}{7}+\frac{7}{10}.\frac{8}{7}\)

\(=\frac{6}{7}.\left(\frac{-15}{20}+\frac{1}{20}\right)+\frac{4}{5}\)

\(=\frac{6}{7}.\frac{-7}{10}+\frac{4}{5}\)

\(=-\frac{3}{5}+\frac{4}{5}\)

\(=\frac{1}{5}\)

Linz

a) (-8)+10+(-12)+14+...+(-32)+34+(-36)+38 

=(-8+10)+(-12+14)+...+(-32+34)+(-36+38)

=2+2+...+2+2 ( Có 16 số 2)

=2.16

=32

Trả lời:

\(a)\)\(\left(-8\right)+10+\left(-12\right)+14+...+\left(-32\right)+34+\left(-36\right)+38\)(Có 16 số)

\(=\left[\left(-8\right)+10\right]+\left[\left(-12\right)+14\right]+...+\left[\left(-36\right)+38\right]\)(Có 8 nhóm)

\(=\left(-2\right)+\left(-2\right)+...+\left(-2\right)\)

\(=\left(-2\right).8\)

\(=-16\)

\(b,\)\(1+3+5+...+49-2-4-6-...-50\)

\(=\left(1-2\right)+\left(3-4\right)+...+\left(49-50\right)\)(Có 25 nhóm)

\(=\left(-1\right)+\left(-1\right)+...+\left(-1\right)\)

\(=\left(-1\right).25\)

\(=-25\)

Hok tốt!

Good girl

( 2 x y + 2/15 ) x 3 = 4/5

( 2 x y + 2/15 )      = 4/5 : 3 

( 2 x y + 2/15 )      =   4/15

 2 x y                    = 4/15 - 2/15 

2 x y                     =     2/15

     y                      =     2/15 :2 

   y                          =    1/15

(2 x y + 2/15) x 3 = 4/5 

2 x y + 2/15) = 4/5 : 3 

2 x y + 2/15 = 4/15 

2 x y = 4/15 - 2/15 

2 x y = 2/15 

y = 2/15 : 2 

y = 1/15 

7/9 x (2 - 1/3 x y) = 14/15 

(2 - 1/3 x y) = 14/15 : 7/9 

(2 - 1/3 x y) = 6/5 

2 - y = 6/5 x 1/3 

2 - y = 2/5 

y = 2/5 + 2 

y = 12/5 

4/21 + 5 x y - 8/7 = 1/3 

4/21 + 5 x y = 1/3 + 8/7 

4/21 + 5 x y = 31/21 

5 x y = 31/21 - 4/21 

5 x y = 9/7 

y = 9/7 : 5 

y = 9/35 

7/12 x y - 3/12 x y = 5 

y x (7/12 - 3/12) = 5 

y x 1/3 = 5 

y = 5 : 1/3 

y = 15 

Trung bình mỗi em học sinh cao số cm lag

      (148 + 146 +144 + 142 + 140 ) : 5 = 144 (cm)

           Đáp số: 144 cm

Bài 1 : 

a) A= (1;2;3;4;5)

b) B= ( 63;64;65;66;67;68;69;70)

Bài 2 :

a) 10x-5 = 11.5-10

10x-5 = 55-10

10x=45+5

10x=50

x=5

b) 27-3x=9.2-3

27-3x = 18-3

27-3x=15

3x=27-15

3x=12

x=4

c) 4x-15=12:12

4x-15=1

4x=16

x=4

d) 2+13x=14.2

13x=28-2

13x=26

x=2

a) \(10x-5=45\)

\(10x=40\)

\(x=4\)

b) \(27-3x=15\)

\(3x=27-15=12\)

\(x=\dfrac{12}{3}=4\)

c) \(4x-15=1\)

\(4x=16\)

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

d) \(2+13x=28\)

\(13x=26\)

\(x=\dfrac{26}{13}=2\)

Bài 1:

a) \(A=\left\{0;1;2;3;4;5\right\}\)

b) \(B=\left\{63;64;65;66;67;68;69;70\right\}\)

Bài 2:

a) \(10x-5=11.5-10\)

\(10x-5=55-10=45\)

\(10x=45+5\)

\(10x=50\)

\(x=50:10\)

\(x=5\)

b) \(27-3x=9.2-3\)

\(27-3x=18-3=15\)

\(3x=27-15\)

\(3x=12\)

\(x=12:3\)

\(x=4\)

c) \(4x-15=12:12\)

\(4x-15=1\)

\(4x=1+15\)

\(4x=16\)

\(x=16:4\)

\(x=4\)

d) \(2+13x=14.2\)

\(2+13x=28\)

\(13x=28-2\)

\(13x=26\)

\(x=26:13\)

\(x=2\)

\(#WendyDang\)

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