a: \(=3\cdot7\sqrt{3}+2\cdot6\sqrt{3}-4\cdot4\sqrt{3}-11\sqrt{3}\)

\(=21\sqrt{3}+12\sqrt{3}-16\sqrt{3}-11\sqrt{3}\)

\(=6\sqrt{3}\)

b: \(=\sqrt{\left(3-\sqrt{5}\right)^2}+\sqrt{\left(\sqrt{5}-1\right)^2}\)

\(=3-\sqrt{5}+\sqrt{5}-1\)

=2

c: \(=\left(4-\sqrt{3}\right)\sqrt{\left(4+\sqrt{3}\right)^2}\)

\(=\left(4-\sqrt{3}\right)\left(4+\sqrt{3}\right)\)

=16-3

=13

4) 121

5) - 32

6) 48

7) - 137

8) - 280

9) - 36

10) 42

4) 41

5) -32

6)  48

7) -137

8) -280

9) -36

10) 42

\(107-\left\{38+\left[7.3^2-24:6+\left(9-7\right)^3\right]\right\}:15\)

\(=107-\left\{38+\left[7.3^2-24:6+2^3\right]\right\}:15\)

\(=107-\left\{38+\left[7.3^2-4+2^3\right]\right\}:15\)

\(=107-\left\{38+\left[63-4+2^3\right]\right\}:15\)

\(=107-\left\{38+\left[59+2^3\right]\right\}:15\)

\(=107-\left\{38+67\right\}:15\)

\(=107-105:15\)

\(=107-7\)

\(=100\)

107 – {38 + [7.3² – 24 : 6+(9 – 7)³]}:15

= 107 - {38+ [7.3² - 24 : 6 + 2³ ]} : 15

= 107 - {38 + [ 7.9 - 24 : 6 + 8]} :15

= 107 - {38+[ 63 - 4 + 8]} : 15

= 107 - {38 + 67} : 15

= 107 - 105 : 15

= 107 - 7

= 100

17) 10 – [(8² – 48).5 + (2³.10 + 8)] : 28 - 7⁰

    = 10 - [(64 - 48).5 + (8.10 +8)] : 28 - 7⁰

    = 10 - [16.5 + 88] : 28 - 7⁰

    = 10 - [80 + 88] : 28 - 7⁰

    = 10 - 168 : 28 - 7⁰

    = 10 - 6 - 1

    = 3

nếu sai câu nào mong bạn thông cảm ^^

a) 

x − 15 17 = − 2 9 . − 9 17 x − 15 17 = 2 17 x = 2 17 + 15 17 x = 1

b)

x − ( − 3 ) . 9 ( − 12 ) = 6 8 x − 9 4 = 6 8 x = 6 8 + 9 4 x = 3  

\(A=\sqrt{12}+2\sqrt{27}+3\sqrt{45}-9\sqrt{48}\)

\(=2\sqrt{3}+6\sqrt{3}+9\sqrt{5}-36\sqrt{3}\)

\(=9\sqrt{5}-28\sqrt{3}\)

\(B=\left(\sqrt{48}-2\sqrt{75}+\sqrt{108}-\sqrt{147}\right):\sqrt{3}\)

\(=4-2\cdot5+6-7\)

\(=4-10+6-7\)

=-7

A=\(\sqrt{12}\)+2\(\sqrt{27}\)+3\(\sqrt{45}\) -9\(\sqrt{48}\)

  =\(\sqrt{4.3}\) +2\(\sqrt{9.3}\)+3\(\sqrt{9.5}\) -9\(\sqrt{16.3}\)

  =2\(\sqrt{3}\) +6\(\sqrt{3}\)+9\(\sqrt{5}\) -36\(\sqrt{3}\)

   =\(\sqrt{3}\)(2+6-36) + 9\(\sqrt{5}\)

   =9\(\sqrt{5}\)- 28\(\sqrt{3}\)

mấy bạn ghi cách viết giùm mình

cảm ơn

4) 87+(-45)-(-79)=  87 + ( -45 ) + 79 = 121

5) (-15)+45-62=  30 - 62 = -32

6) 120: (-5)+72=  -24 + 72 = 48

7) -147-130: (-13)= -147 - ( -10 ) = -137

8) 125. (-8) : (-25). (-7)= -1000 : (-25) (-7)= -280

9) 25-18+(-43) = 7 + ( -43) = -36

10) -18-3.(-20)= -18-( -60) = 42

Bài 1:

Ta thấy:

\(\frac{1}{2}>\frac{1}{6};\frac{1}{3}>\frac{1}{6};\frac{1}{4}>\frac{1}{6};\frac{1}{5}>\frac{1}{6};\frac{1}{6}=\frac{1}{6}\)

\(=>\frac{1}{2}+\frac{1}{3}+\frac{1}{4}+\frac{1}{5}+\frac{1}{6}>\frac{1}{6}+\frac{1}{6}+\frac{1}{6}+\frac{1}{6}+\frac{1}{6}\)

\(=>\frac{1}{2}+\frac{1}{3}+\frac{1}{4}+\frac{1}{5}+\frac{1}{6}>\frac{5}{6}\)

Bài 2:

Đặt \(A=\frac{1}{5}+\frac{1}{45}+\frac{1}{117}+...+\frac{1}{1517}\)

Ta thấy \(\frac{1}{5}=\frac{1}{1.5};\frac{1}{45}=\frac{1}{5.9};\frac{1}{117}=\frac{1}{9.13}\)

Theo quy luật như vậy ta có các số tiếp theo là:

\(\frac{1}{13.17}=\frac{1}{221};\frac{1}{17.21}=\frac{1}{357};\frac{1}{21.25}=\frac{1}{525};\frac{1}{25.29}=\frac{1}{725};...\)

Ta có \(A=\frac{1}{5}+\frac{1}{45}+\frac{1}{117}+...+\frac{1}{1517}\)

\(=>A=\frac{1}{1.5}+\frac{1}{5.9}+\frac{1}{9.13}+...+\frac{1}{27.31}\)

\(=>4A=\frac{4}{1.5}+\frac{4}{5.9}+\frac{4}{9.13}+...+\frac{4}{27.31}\)

\(=>4A=\frac{5-1}{1.5}+\frac{9-5}{5.9}+\frac{13-9}{9.13}+...+\frac{31-27}{27.31}\)

\(=>4A=\frac{5}{1.5}-\frac{1}{1.5}+\frac{9}{5.9}-\frac{5}{5.9}+\frac{13}{9.13}-\frac{9}{9.13}+...+\frac{31}{27.31}-\frac{27}{27.31}\)

\(=>4A=1-\frac{1}{5}+\frac{1}{5}-\frac{1}{9}+\frac{1}{9}-\frac{1}{13}+...+\frac{1}{27}-\frac{1}{31}\)

\(=>4A=1-\frac{1}{31}=\frac{30}{31}=>A=\frac{30}{31}.\frac{1}{4}=\frac{15}{62}\)

a,    {-5}³ +2012 + |-3|+2.{-3}

= -125 + 2010 + 3 - 6

= 1885 + 3 - 6

= 1888 - 6

= 1882

b,     {-25}.{35+147}+ 35 .{25+147}

=-25.35+(-25).147+35.25+35.147

=35.[-25+25+147]+(-25).147

=35.147+(-25).147

=147.[35+(-25)]

=147.10

=1470

a,    {-5}^3 +2012 + |-3|+2.{-3}

= -125+2012+3-6

=(-125+3)+(2012-6)

=-122+2006

=1884

b,     {-25}.{35+147}+ 35 .{25+147}

=-25.35-25.147+35.25+35.147

=(-25.35+35.25)+(-25.147+35.147)

=0+147(-25+35)

=0+147.10

=1470