a)16. x² = 64

x² = 64 : 16

x² = 4

x² = 2²

⇒ x = 2

b) (5.x - 2) - 64 = -36

(5.x - 2) = -36 + 64

5.x - 2 = 28

5.x = 28 + 2

5.x = 30

x = 30 : 5

x = 6

c) (2x - 10).(5 - x) = 0

TH1: 2x - 10 = 0

         2x = 0 + 10

         2x = 10

           x = 10 : 2

           x = 5

TH2: 5 - x = 0

              x = 5 - 0

              x = 5

⇒ Vậy x = 5.

cứu tui

\(16.x^2=64\)

\(=>x^2=64:16\)

\(=>x^2=4\)

\(=>x=2\) hoặc \(x=-2\)

_______

\(\left(5x-2\right)-64=-36\)

\(=>5x-2=\left(-36\right)+64\)

\(=>5x-2=28\)

\(=>5x=28+2\)

\(=>5x=30\)

\(=>x=30:5\)

\(=>x=6\)

_______

\(\left(2x-10\right).\left(5-x\right)=0\)

TH1: \(2x-10=0\)

\(=>2x=0+10\)

\(=>2x=10\)

\(=>x=10:2\)

\(=>x=5\)

TH2: \(5-x=0\)

\(x=5-0\)

\(x=5\)

\(=>x=5\)

mai mình thi rồi, các bạn giúp mình với

Chờ tí

Câu 4: 

d) Ta có: \(\dfrac{-2}{17}+\dfrac{3}{19}+\dfrac{-15}{17}+\dfrac{16}{19}+\dfrac{5}{6}\)

\(=\left(-\dfrac{2}{17}-\dfrac{15}{17}\right)+\left(\dfrac{3}{19}+\dfrac{16}{19}\right)+\dfrac{5}{6}\)

\(=-1+1+\dfrac{5}{6}=\dfrac{5}{6}\)

Câu 3:

a) \(\dfrac{12}{36}=\dfrac{12:12}{36:12}=\dfrac{1}{3}\)

\(\dfrac{-16}{20}=\dfrac{-16:4}{20:4}=\dfrac{-4}{5}\)

b) \(\dfrac{21}{105}=\dfrac{21:21}{105:21}=\dfrac{1}{5}\)

\(\dfrac{35}{150}=\dfrac{35:5}{150:5}=\dfrac{7}{30}\)

Câu 4: 

a) \(\dfrac{3}{10}+\dfrac{5}{10}=\dfrac{3+5}{10}=\dfrac{8}{10}=\dfrac{4}{5}\)

b) Ta có: \(\left(-27\right)\cdot36+64\cdot\left(-27\right)+23\cdot\left(-100\right)\)

\(=\left(-27\right)\cdot\left(64+36\right)+23\cdot\left(-100\right)\)

\(=-27\cdot100-23\cdot100\)

\(=100\left(-27-23\right)\)

\(=-50\cdot100=-5000\)

c) \(\dfrac{5}{8}+\dfrac{3}{12}=\dfrac{15}{24}+\dfrac{6}{24}=\dfrac{21}{24}=\dfrac{7}{8}\)

d) Ta có: \(\dfrac{-2}{17}+\dfrac{3}{19}+\dfrac{-15}{17}+\dfrac{16}{19}+\dfrac{5}{6}\)

\(=\left(-\dfrac{2}{17}+\dfrac{-15}{17}\right)+\left(\dfrac{3}{19}+\dfrac{16}{19}\right)+\dfrac{5}{6}\)

\(=-1+1+\dfrac{5}{6}\)

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

\(\dfrac{4^9\cdot36+64^4}{100\cdot16^4}=\dfrac{2^{20}\cdot3^2+2^{24}}{2^{18}\cdot5^2}=\dfrac{2^{20}\left(3^2+2^4\right)}{2^{18}\cdot5^2}=4\)

 ko bt

2^(10 : 64 x 16) = 2^[(10 x 16) : 64] = 2^(160 : 64) = 2^25

2^(10 x 8) = 2^80     3^(5 : 27) = 3^(5/27)     5^(2 x 125) = 5^250     6^(6 : 36) = 6^(1/6)

1/5+4/10+9/15+25/25+36/30+49/35+64/40+81/45

=1/5 + (4/10:2) +  (9/15:3)+25/25  +  (36/30:6)+  (49/35:7) +  (64/40:8)  +  (81/45:9)

=1/5 + 1/5 + 1/5 + 1 + 1/5 + 1/5 + 1/5 + 1/5

=1/5 x 7 + 1

=12/5

Có tính nhanh ko?

\(\frac{1}{5}+\frac{4}{10}+\frac{9}{15}+\frac{16}{20}+1+\frac{36}{30}+\frac{49}{35}+\frac{64}{40}+\frac{81}{45}\)

\(=\left(\frac{1}{5}+\frac{81}{45}\right)+\left(\frac{4}{10}+\frac{49}{35}\right)+\left(\frac{9}{15}+\frac{49}{35}\right)+\left(\frac{16}{20}+\frac{36}{30}\right)+1\)

\(=2+2+2+2+1\)

\(=2\times4+1\)

\(=9\)

~ Hok tốt ~

Ta có: \(\dfrac{1}{5}+\dfrac{4}{10}+\dfrac{9}{15}+\dfrac{16}{20}+\dfrac{25}{25}+\dfrac{36}{30}+\dfrac{49}{35}+\dfrac{64}{40}+\dfrac{81}{45}\)

\(=\dfrac{1}{5}+\dfrac{2}{5}+\dfrac{3}{5}+\dfrac{4}{5}+\dfrac{5}{5}+\dfrac{6}{5}+\dfrac{7}{5}+\dfrac{8}{5}+\dfrac{9}{5}\)

\(=\dfrac{45}{5}=9\)

\(\dfrac{1}{5}+\dfrac{4}{10}+\dfrac{9}{15}+...+\dfrac{81}{45}\\ =\dfrac{1}{5}+\dfrac{2}{5}+\dfrac{3}{5}+...+\dfrac{9}{15}\\ =\dfrac{\left(1+2+3+...+9\right)}{15}=\dfrac{\left(1+9\right)x9:2}{15}\\ =\dfrac{10x9:2}{15}=\dfrac{45}{15}=3\)