\(\sqrt{27}+\sqrt{75}-\sqrt{\dfrac{1}{3}}\)

b)

K
Khách

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6 tháng 6 2017

#Giải:

a)\(\sqrt{27}\)+\(\sqrt{75}\)-\(\sqrt{\dfrac{1}{3}}\)=8\(\sqrt{3}\)-\(\sqrt{\dfrac{1}{3}}\)=\(\dfrac{23\sqrt{3}}{3}\).

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

c)\(\dfrac{3}{\sqrt{7}+\sqrt{2}}\)+\(\dfrac{2}{3+\sqrt{7}}\)+\(\dfrac{2-\sqrt{2}}{\sqrt{2}-1}\)=1,093+\(\dfrac{2-\sqrt{2}}{\sqrt{2}-1}\)=2,507.

7 tháng 6 2017

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

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

= \(\dfrac{23\sqrt{3}}{3}\)

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

= \(1+\sqrt{3}-\left(\sqrt{3}-1\right)\)

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

= 2

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

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

= \(\dfrac{3\sqrt{7}-3\sqrt{2}}{5}+3-\sqrt{7}+\sqrt{2}\)

= \(\dfrac{3\sqrt{7}-3\sqrt{2}-5\sqrt{7}+5\sqrt{2}}{5}+3\)

= \(\dfrac{-2\sqrt{7}+2\sqrt{2}}{5}+3\)

\(\approx2,5\)

22 tháng 7 2017

bn lấy máy tính mà tính ý

22 tháng 7 2017

Bài1:

Ta có:

a)\(\sqrt{\dfrac{3^2}{5^2}}=\sqrt{\dfrac{9}{25}}=\dfrac{3}{5}\)

b)\(\dfrac{\sqrt{3^2}+\sqrt{42^2}}{\sqrt{5^2}+\sqrt{70^2}}=\dfrac{\sqrt{9}+\sqrt{1764}}{\sqrt{25}+\sqrt{4900}}=\dfrac{3+42}{5+70}=\dfrac{45}{75}=\dfrac{3}{5}\)

c)\(\dfrac{\sqrt{3^2}-\sqrt{8^2}}{\sqrt{5^2}-\sqrt{8^2}}=\dfrac{\sqrt{9}-\sqrt{64}}{\sqrt{25}-\sqrt{64}}=\dfrac{3-8}{5-8}=\dfrac{-5}{-3}=\dfrac{5}{3}\)

Từ đó, suy ra: \(\dfrac{3}{5}=\sqrt{\dfrac{3^2}{5^2}}=\dfrac{\sqrt{3^2}+\sqrt{42^2}}{\sqrt{5^2}+\sqrt{70^2}}\)

Bài 2:

Không có đề bài à bạn?

Bài 3:

a)\(\sqrt{x}-1=4\)

\(\Rightarrow\sqrt{x}=5\)

\(\Rightarrow x=\sqrt{25}\)

\(\Rightarrow x=5\)

b)Vd:\(\sqrt{x^4}=\sqrt{x.x.x.x}=x^2\Rightarrow\sqrt{x^4}=x^2\)

Từ Vd suy ra:\(\sqrt{\left(x-1\right)^4}=16\)

\(\Rightarrow\left(x-1\right)^2=16\)

\(\Rightarrow\left(x-1\right)^2=4^2\)

\(\Rightarrow x-1=4\)

\(\Rightarrow x=5\)

25 tháng 10 2022

a: \(=2\cdot\dfrac{5}{4}-3\cdot\dfrac{7}{6}+4\cdot\dfrac{9}{8}=\dfrac{5}{2}-\dfrac{7}{2}+\dfrac{9}{2}=\dfrac{7}{2}\)

b: \(=18-16\cdot\dfrac{1}{2}+\dfrac{1}{16}\cdot\dfrac{3}{4}\)

=10+3/64

=643/64

c: \(=\dfrac{2}{3}\cdot\dfrac{9}{4}-\dfrac{3}{4}\cdot\dfrac{8}{3}+\dfrac{7}{5}\cdot\dfrac{5}{14}=\dfrac{3}{2}-2+\dfrac{1}{2}=2-2=0\)

25 tháng 10 2022

a: \(=7\cdot\dfrac{6}{7}-5+\dfrac{3\sqrt{2}}{2}=1+\dfrac{3}{2}\sqrt{2}\)

b: \(=-\dfrac{8}{7}-\dfrac{3}{5}\cdot\dfrac{5}{8}+\dfrac{1}{2}=\dfrac{-16+7}{14}-\dfrac{3}{8}=\dfrac{-9}{14}-\dfrac{3}{8}\)

\(=\dfrac{-72-42}{112}=\dfrac{-114}{112}=-\dfrac{57}{56}\)

c: \(=20\sqrt{5}-\dfrac{1}{4}\cdot\dfrac{4}{3}+\dfrac{3}{2}=20\sqrt{5}+\dfrac{3}{2}-\dfrac{1}{3}=20\sqrt{5}+\dfrac{7}{6}\)

 

18 tháng 7 2017

a)\(\sqrt{\dfrac{3^2}{7^2}}=\sqrt{\dfrac{9}{49}}=\sqrt{\dfrac{3}{7}}\)

b)\(\dfrac{\sqrt{3^2}+\sqrt{39^2}}{\sqrt{7^2}+\sqrt{91^2}}=\dfrac{\sqrt{9}+\sqrt{1521}}{\sqrt{49}+\sqrt{8281}}=\dfrac{3+39}{7+91}=\dfrac{42}{98}\)

c)Tương tự câu b, ta đc:

\(\dfrac{\sqrt{3^2}-\sqrt{39^2}}{\sqrt{7^2}-\sqrt{91^2}}=\dfrac{3-39}{7-91}=\dfrac{-36}{86}=\dfrac{3}{7}\)

d)Tương tự câu a, ta đc:

\(\dfrac{\sqrt{39^2}}{\sqrt{91^2}}=\dfrac{39}{91}\)

Chúc Bạn Học Tốt!!!

18 tháng 7 2017

a) \(\sqrt{\dfrac{3^2}{7^2}}=\sqrt{\left(\dfrac{3}{7}\right)^2}=\left|\dfrac{3}{7}\right|=\dfrac{3}{7}\)

b) \(\dfrac{\sqrt{3}^2+\sqrt{39}^2}{\sqrt{7}^2+\sqrt{91}^2}=\dfrac{\left|3\right|+\left|39\right|}{\left|7\right|+\left|91\right|}=\dfrac{3+39}{7+91}=\dfrac{42}{98}=\dfrac{3}{7}\)

c) \(\dfrac{\sqrt{3}^2-\sqrt{39}^2}{\sqrt{7}^2-\sqrt{91}^2}=\dfrac{\left|3\right|- \left|39\right|}{\left|7\right|-\left|91\right|}=\dfrac{3-39}{7-91}=\dfrac{-36}{-84}=\dfrac{3}{7}\)

d) \(\sqrt{\dfrac{39^2}{91^2}}=\sqrt{\left(\dfrac{39}{91}\right)^2}=\left|\dfrac{39}{91}\right|=\dfrac{39}{91}=\dfrac{3}{7}\)

27 tháng 7 2018

B1

a. = 7/3. ( 37/5 - 32/5)

= 7/3 . 1

= 7/3

humPhần b có gì đó sai sao lại có 3:+

c. = 4 + 6 - 3 + 5

= 12

d. = -5/21 : -19/21 : 4/5

= 25/76

B2

a. 1/4 : x =1/2 - 3/4

x = -1/4

x = 1/4 : -1/4

x = -1

b. 2 . | 2x - 3 | = 4 - (-8)

2 . | 2x - 3| = 12

| 2x - 3 | = 12:2

| 2x - 3 | = 6

| x - 3 | = 6:2

| x - 3 | = 3

=> x - 3 = +- 3

* x - 3 = 3

x = 6

* x - 3 = -3

x = 0

Chúc bạn vui vẻ yeu

28 tháng 7 2018

b. = 3 : 9/4 + 1/9 .6

= 4/3 + 2/3

= 2

30 tháng 10 2017

1.

0,2 . \(\sqrt{100}\) - \(\sqrt{\dfrac{16}{25}}\)

= 0,2 . 10 - \(\dfrac{4}{5}\)

= 2 - \(\dfrac{4}{5}\)

= \(\dfrac{6}{5}\)

30 tháng 10 2017

1/ \(0,2.\sqrt{100}-\sqrt{\dfrac{16}{25}}\)

\(=0,2.10-0,8\)

\(=2-0,8=1,2\)

2/ \(\dfrac{2^7.9^3}{6^5.8^2}\)

\(=\dfrac{93312}{497664}=\dfrac{3}{16}=0,1875\)

3/ \(\sqrt{0,01}-\sqrt{0,25}\)

\(=0,1-0,5\)

\(=-0,4\)

4/ \(0,5.\sqrt{100}-\sqrt{\dfrac{1}{4}}\)

\(=0,5.10-0,5\)

\(=5-0,5=4,5\)

5/ \(7.\sqrt{0,01}+2.\sqrt{0,25}\)

\(=7.0,1+2.0,5\)

\(=0,7+1=1,7\)

6/ \(0,5.\sqrt{100}-\sqrt{\dfrac{1}{25}}\)

\(=0,5.10-0,2\)

\(=5-0,2=4,8\)

21 tháng 9 2017

a)\(\sqrt{1}\)+\(\sqrt{9}\)+\(\sqrt{25}\)+\(\sqrt{49}\)+\(\sqrt{81}\)

=1+3+5+7+9

=25

b)=\(\dfrac{1}{2}\)+\(\dfrac{1}{3}\)+\(\dfrac{1}{6}\)+\(\dfrac{1}{4}\)

=\(\dfrac{6}{12}\)+\(\dfrac{4}{12}\)+\(\dfrac{2}{12}\)+\(\dfrac{3}{12}\)

=\(\dfrac{15}{12}\)

c) =0,2+0.3+0,4

= 0.9

d) =9-8+7

=8

j) =1,2-1,3+1.4

= (-0,1)+1,4

=1,4

g) \(\dfrac{2}{5}\)+\(\dfrac{5}{2}\)+\(\dfrac{9}{10}\)+\(\dfrac{3}{4}\)

= (\(\dfrac{4}{10}\)+\(\dfrac{15}{10}\)+\(\dfrac{9}{10}\))+\(\dfrac{3}{4}\)

= \(\dfrac{14}{5}\)+\(\dfrac{3}{4}\)

=\(\dfrac{56}{20}\)+\(\dfrac{15}{20}\)

= \(\dfrac{71}{20}\)

Nhớ tick cho mk nha~

22 tháng 10 2018

Tính:

C = \(3\dfrac{1}{2}.\dfrac{4}{49}-\left[2,\left(4\right).2\dfrac{5}{11}\right]:\left(\dfrac{-42}{5}\right)\)

= \(\dfrac{7}{2}.\dfrac{4}{49}-\left[\left(2+0,\left(1\right).4\right).\dfrac{27}{5}\right].\dfrac{-5}{42}\)

= \(\dfrac{1.2}{1.7}-\left[\left(2+\dfrac{1.4}{9}\right).\dfrac{27}{5}\right].\dfrac{-5}{42}\)

= \(\dfrac{2}{7}-\left[\dfrac{18+4}{9}.\dfrac{27}{5}\right].\dfrac{-5}{42}\)

= \(\dfrac{2}{7}-\left[\dfrac{22.9}{3.5}\right].\dfrac{-5}{42}\)

= \(\dfrac{2}{7}-\dfrac{198}{15}.\dfrac{-5}{42}=\dfrac{2}{7}-\dfrac{11}{3}.\dfrac{-1}{7}\)

= \(\dfrac{2}{7}+\dfrac{11}{21}\) = \(\dfrac{6+11}{21}\) = \(\dfrac{17}{21}\)

22 tháng 10 2018

Bạn cóa thể giải giúp mình câu B ko?bucminhngaingung