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

b: \(=2\sqrt{2}+2\sqrt{2}+5\sqrt{2}=9\sqrt{2}\)

c: \(=4\sqrt{3}+3\sqrt{3}-3\sqrt{5}+2\sqrt{5}=7\sqrt{3}-\sqrt{5}\)

d: \(=5\sqrt{3}+4\sqrt{3}-10\sqrt{3}=-\sqrt{3}\)

e: \(=\left(\sqrt{7}-2\sqrt{3}\right)\cdot\sqrt{7}+2\sqrt{21}\)

=7-2*căn 21+2*căn 21

=7

f: \(=\left(2\sqrt{11}-3\sqrt{2}\right)\cdot\sqrt{11}+3\sqrt{22}\)

=22-3*căn 22+3*căn 22

=22

a) \(3\sqrt{5}+\sqrt{20}-2\sqrt{5}\)

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

\(=3\sqrt{5}\)

b) \(2\sqrt{2}+\sqrt{8}+\sqrt{50}\)

\(=2\sqrt{2}+2\sqrt{2}+5\sqrt{2}\)

\(=9\sqrt{5}\)

c) \(4\sqrt{3}+\sqrt{27}-\sqrt{45}+2\sqrt{5}\)

\(=4\sqrt{3}+3\sqrt{3}-3\sqrt{5}+2\sqrt{5}\)

\(=7\sqrt{3}-\sqrt{5}\)

d) \(\sqrt{75}+\sqrt{48}-\sqrt{300}\)

\(=5\sqrt{3}+4\sqrt{3}-10\sqrt{3}\)

\(=-\sqrt{3}\)

e) \(\left(\sqrt{28}-\sqrt{12}-\sqrt{7}\right)\sqrt{7}+2\sqrt{21}\)

\(=\left(2\sqrt{7}-2\sqrt{3}-\sqrt{7}\right)\sqrt{7}+2\sqrt{21}\)

\(=\left(\sqrt{7}-2\sqrt{3}\right)\sqrt{7}+2\sqrt{21}\)

\(=7-2\sqrt{21}+2\sqrt{21}\)

\(=7\)

f) \(\left(\sqrt{99}-\sqrt{18}-\sqrt{11}\right)\sqrt{11}+3\sqrt{22}\)

\(=\left(3\sqrt{11}-3\sqrt{2}-\sqrt{11}\right)\sqrt{11}+3\sqrt{22}\)

\(=\left(2\sqrt{11}-3\sqrt{2}\right)\sqrt{11}+3\sqrt{22}\)

\(=22-3\sqrt{22}+3\sqrt{22}\)

\(=22\)

g) \(3\sqrt{45}-5\sqrt{125x}+7\sqrt{20x}+28\)

\(=9\sqrt{5}-25\sqrt{5x}+14\sqrt{5x}+28\)

\(=9\sqrt{5}-11\sqrt{5x}+28\)

a) \(\sqrt{12}+5\sqrt{3}-\sqrt{48}=\sqrt{2^2\cdot3}+5\sqrt{3}-\sqrt{4^2\cdot3}\)

\(=2\sqrt{3}+5\sqrt{3}-4\sqrt{3}=\left(2+5-4\right)\sqrt{3}=3\sqrt{3}\)

b) \(5\sqrt{5}+\sqrt{20}-3\sqrt{45}=5\sqrt{5}+\sqrt{2^2\cdot5}-3\sqrt{3^2\cdot5}\) \(=5\sqrt{5}+2\sqrt{5}-9\sqrt{5}=-2\sqrt{5}\)

c)

\(2\sqrt{32}+4\sqrt{8}-5\sqrt{18}=2\sqrt{4^2\cdot2}+4\sqrt{2^2\cdot2}-5\sqrt{3^2\cdot2}\) \(=8\sqrt{2}+8\sqrt{2}-15\sqrt{2}=\sqrt{2}\)

d)\(\sqrt{2^2\cdot3}+\sqrt{5^2\cdot3}-\sqrt{3^2\cdot3}=2\sqrt{3}+5\sqrt{3}-3\sqrt{3}=4\sqrt{3}\)

Mọi người ơi, giúp em với ạ

a) \(\left(9^4.8+9^4.5\right):\left(9^2.\left(10-1\right)\right)\)

=\(9^4.13:9^3=13.9=117\)

b) 100-(75-25)=100-50=50

`@` `\text {Ans}`

`\downarrow`

`a)`

\(\left(\dfrac{7}{8}-\dfrac{3}{4}\right)\cdot1\dfrac{1}{3}-\dfrac{2}{3}\cdot0,5\)

`=`\(\dfrac{1}{8}\cdot\dfrac{4}{3}-\dfrac{1}{3}\)

`=`\(\dfrac{1}{6}-\dfrac{1}{3}=-\dfrac{1}{6}\)

`b)`

\(\left(2+\dfrac{5}{6}\right)\div1\dfrac{1}{5}+\left(-\dfrac{7}{12}\right)\)

`=`\(\dfrac{17}{6}\div1\dfrac{1}{5}-\dfrac{7}{12}\)

`=`\(\dfrac{85}{36}-\dfrac{7}{12}=\dfrac{16}{9}\)

`c)`

\(75\%-1\dfrac{1}{2}+0,5\div\dfrac{5}{12}\)

`=`\(-\dfrac{3}{4}+\dfrac{6}{5}=\dfrac{9}{20}\)

a) \(\left(\dfrac{7}{8}-\dfrac{3}{4}\right).1\dfrac{1}{3}-\dfrac{2}{3}.0,5\)

\(=\left(\dfrac{7}{8}-\dfrac{6}{8}\right).\dfrac{4}{3}-\dfrac{2}{3}.\dfrac{1}{2}\)

\(=\dfrac{1}{8}.\dfrac{4}{3}-\dfrac{2}{3}.\dfrac{1}{2}\)

\(=\dfrac{1}{6}-\dfrac{1}{3}\)

\(=\dfrac{-1}{6}\)

b) \(\left(2+\dfrac{5}{6}\right):1\dfrac{1}{5}+\dfrac{-7}{12}\)

\(=\left(\dfrac{12}{6}+\dfrac{5}{6}\right):\dfrac{6}{5}+\dfrac{-7}{12}\)

\(=\dfrac{17}{6}.\dfrac{5}{6}+\dfrac{-7}{12}\)

\(=\dfrac{85}{36}+\dfrac{-7}{12}\)

\(=\dfrac{16}{9}\)

c) \(75\%-1\dfrac{1}{2}+0,5:\dfrac{5}{12}\)

\(=\dfrac{3}{4}-\dfrac{3}{2}+\dfrac{1}{2}.\dfrac{12}{5}\)

\(=\dfrac{3}{4}-\dfrac{6}{4}+\dfrac{6}{5}\)

\(=\dfrac{-3}{4}+\dfrac{6}{5}\)

\(=\dfrac{9}{20}\)

a) Ta có: \(A=\dfrac{2}{7}+\dfrac{-3}{8}+\dfrac{11}{7}+\dfrac{1}{3}+\dfrac{1}{7}+\dfrac{5}{-8}\)

\(=\left(\dfrac{2}{7}+\dfrac{11}{7}+\dfrac{1}{7}\right)+\left(\dfrac{-3}{8}+\dfrac{-5}{8}\right)+\dfrac{1}{3}\)

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

\(=1+\dfrac{1}{3}=\dfrac{4}{3}\)

b) Ta có: \(B=\dfrac{-3}{8}+\dfrac{12}{25}+\dfrac{5}{-8}+\dfrac{2}{-5}+\dfrac{13}{25}\)

\(=\left(\dfrac{-3}{8}+\dfrac{-5}{8}\right)+\left(\dfrac{12}{25}+\dfrac{13}{25}\right)+\dfrac{-2}{5}\)

\(=-1+1+\dfrac{-2}{5}\)

\(=-\dfrac{2}{5}\)

Giải:

A= 2/7+ -3/8 +11/7 +1/3 + 1/7 + 5/-8

A= (2/7+11/7+1/7)+(-3/8+-5/8)+1/3

A= 2+ (-1) + 1/3

A= 1+1/3

A= 4/3

B= -3/8 + 12/25 + 5/-8 + 2/-5 + 13/25

B= (-3/8+-5/8) + (12/25+13/25) + -2/5

B= -1 + 1 + -2/5

B=-2/5

Chúc bạn học tốt!

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CÁC EM  TỰ LÀ ĐI MẤY BÀI NÀY DỄ LĂM CHỊ  HỌC LỚP 8 NÊN CHỊ BIẾT NHƯNG ĐỪNG BẢO CHỊ LÀ CHO HAY GỢI Ý CÁCH LÀM NHA.

tìm y: 

y  x 4 - 25 dm = 75 cm

1/ 45. 18 - 5. 9. 28

= 45. 18 - (5. 9) . 28

= 45.18 - 45 .28

= 45. ( 18 - 28)

= 45. ( -10)

= -450

2/ 54 - 6. (12 + 9)

= 54 - 6. 9 + 6. 12

= 54 - 54 + 6. 12

= 0 + 6. 12

= 72