2 | + | 2 | + … + | 2 | = | |
9 x 11 | 11 x 13 | 151 x 153 |
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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!
\(\dfrac{5}{13}\times\dfrac{7}{11}+\dfrac{5}{13}\times\dfrac{2}{11}+\dfrac{8}{13}\times\dfrac{9}{11}\)
\(=\dfrac{5}{13}\times\left(\dfrac{7}{11}+\dfrac{2}{11}\right)+\dfrac{8}{13}\times\dfrac{9}{11}\)
\(=\dfrac{5}{13}\times\dfrac{9}{11}+\dfrac{8}{13}\times\dfrac{9}{11}\)
\(=\dfrac{9}{11}\times\left(\dfrac{5}{13}+\dfrac{8}{13}\right)\)
\(=\dfrac{9}{11}\times1\)
\(=\dfrac{9}{11}\)
a) \(20,23\times21+20,23\times80-20,23\)
\(=20,23\times\left(21+80-1\right)\)
\(=20,23\times100\)
\(=2023\)
\(4.3^{x-1}+2.3^{x+2}=4.3^6+2.3^9\)
\(3^{x-1}.\left(4+2.3^3\right)=3^6.\left(4+2.3^3\right)\)
\(\Leftrightarrow3^{x-1}=3^6\)
\(\Leftrightarrow x-1=6\)
\(\Leftrightarrow x=7\)
Vậy \(x=7\)
\(\frac{5}{9}.\frac{-2}{13}+\frac{5}{13}.\frac{11}{9}-\frac{4}{9}\)
\(=\frac{5}{9}.\frac{-2}{13}+\frac{5}{9}.\frac{-11}{13}-\frac{4}{9}\)
\(=\frac{5}{9}\left(\frac{-2}{13}+\frac{-11}{13}\right)-\frac{4}{9}\)
\(=\frac{5}{9}.-1-\frac{4}{9}\)
\(=\frac{-5}{9}-\frac{4}{9}\)
\(=-1\)
\(\frac{5}{9}\times\frac{-2}{13}+\frac{-5}{13}\times\frac{11}{9}-\frac{4}{9}\)
\(=\frac{2}{9}\times\frac{-5}{13}+\frac{-5}{13}\times\frac{11}{9}-\frac{4}{9}\)
\(=\frac{-5}{13}\times\left(\frac{2}{9}+\frac{11}{9}\right)-\frac{4}{9}\)
\(=\frac{-5}{13}\times\frac{13}{9}-\frac{4}{9}\)
\(=\frac{-5}{9}-\frac{4}{9}\)
\(=\frac{-9}{9}=-1\)
142+21-98+1+2+3+4+5+6+7+8+9x0=
= 1/9 - 1/11 + 1/11 - 1/13 +........+1/151 - 1/153
= 1/9 - 1/153
=16/153