B = (-7) + 9 + (-11) + 13 + ... + (-151) +153

B = [(-7) + 9] + [(-11) + 13 ] + ... + [(-151)+153] 

B =       2     +       2           + ... + 2           (72 chữ số 2)

B = 2*72

b = 144              

Ta có B = [(-7) + 9] + [(-11) +13] + .....+ [(-151)+153]

          B =    2           +       2          + ..... + 2

          B = 72 x 2

          B = 144

          Vậy B = 144

           Bạn k cho mình nhé!

đm thằng Mai Dũng coi vừa thôi

a) = 1.1204
b) = 0.5714

a) = 1.1204
b) = 0.5714

a) = 1.1204
b) = 0.5714

\(\dfrac{5}{13}\times\dfrac{7}{11}+\dfrac{5}{13}\times\dfrac{2}{11}+\dfrac{8}{13}\times\dfrac{9}{11}\)

\(=\dfrac{5}{13}\times\left(\dfrac{7}{11}+\dfrac{2}{11}\right)+\dfrac{8}{13}\times\dfrac{9}{11}\)

\(=\dfrac{5}{13}\times\dfrac{9}{11}+\dfrac{8}{13}\times\dfrac{9}{11}\)

\(=\dfrac{9}{11}\times\left(\dfrac{5}{13}+\dfrac{8}{13}\right)\)

\(=\dfrac{9}{11}\times1\)

\(=\dfrac{9}{11}\)

a) \(20,23\times21+20,23\times80-20,23\)

\(=20,23\times\left(21+80-1\right)\)

\(=20,23\times100\)

\(=2023\)

\(\dfrac{5}{13}\) \(\times\) \(\dfrac{7}{11}\) + \(\dfrac{5}{13}\) \(\times\) \(\dfrac{2}{11}\) + \(\dfrac{8}{13}\) \(\times\) \(\dfrac{9}{11}\)

= \(\left(\dfrac{5}{13}\times\dfrac{7}{11}+\dfrac{5}{13}\times\dfrac{2}{11}\right)\)+ \(\dfrac{8}{13}\) \(\times\) \(\dfrac{9}{11}\)

= \(\dfrac{5}{13}\)\(\times\) (\(\dfrac{7}{11}\) + \(\dfrac{2}{11}\)) + \(\dfrac{8}{13}\) \(\times\) \(\dfrac{9}{11}\)

= \(\dfrac{5}{13}\) \(\times\) \(\dfrac{9}{11}\) + \(\dfrac{8}{13}\) \(\times\) \(\dfrac{9}{11}\)

= \(\dfrac{9}{11}\) \(\times\)( \(\dfrac{5}{13}\) +\(\dfrac{8}{13}\))

= \(\dfrac{9}{11}\) \(\times\) 1

= \(\dfrac{9}{11}\)

Đáp số là 1442/1287 nhé

=\(\dfrac{1442}{1287}\)

=

562 HT

😒😒😒

Trê 

\(4.3^{x-1}+2.3^{x+2}=4.3^6+2.3^9\)

\(3^{x-1}.\left(4+2.3^3\right)=3^6.\left(4+2.3^3\right)\)

\(\Leftrightarrow3^{x-1}=3^6\)

\(\Leftrightarrow x-1=6\)

\(\Leftrightarrow x=7\)

Vậy \(x=7\)

\(5^{x+4}-3.5^{x+3}=2.5^{11}\)

\(\Leftrightarrow5^{x+3}.\left(5-3\right)=2.5^{11}\)

\(\Leftrightarrow5^{x+3}.2=2.5^{11}\)

\(\Leftrightarrow5^{x+3}=5^{11}\)

⇔\(x+3=11\)

\(\Leftrightarrow x=8\)

Vậy \(x=8\)

\(11.6^{x-1}=11.6^{11}+2.6^{13}\)

\(\Rightarrow11.6^{x-1}=6^{11}.\left(11+2.36\right)\)

\(\Rightarrow11.6^{x-1}=6^{11}.83\)

có câu tương tự đó bn

\(\frac{5}{9}.\frac{-2}{13}+\frac{5}{13}.\frac{11}{9}-\frac{4}{9}\)

\(=\frac{5}{9}.\frac{-2}{13}+\frac{5}{9}.\frac{-11}{13}-\frac{4}{9}\)

\(=\frac{5}{9}\left(\frac{-2}{13}+\frac{-11}{13}\right)-\frac{4}{9}\)

\(=\frac{5}{9}.-1-\frac{4}{9}\)

\(=\frac{-5}{9}-\frac{4}{9}\)

\(=-1\)

\(\frac{5}{9}\times\frac{-2}{13}+\frac{-5}{13}\times\frac{11}{9}-\frac{4}{9}\)

\(=\frac{2}{9}\times\frac{-5}{13}+\frac{-5}{13}\times\frac{11}{9}-\frac{4}{9}\)

\(=\frac{-5}{13}\times\left(\frac{2}{9}+\frac{11}{9}\right)-\frac{4}{9}\)

\(=\frac{-5}{13}\times\frac{13}{9}-\frac{4}{9}\)

\(=\frac{-5}{9}-\frac{4}{9}\)

\(=\frac{-9}{9}=-1\)

nhanh lên nhé các bạn ngày mai tớ thi rồi