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\(2^4.5-\left[31-9^2\right]=16.5-\left(31-81\right)=80-\left(-50\right)=130\)
\(2^4\).5-[1.31-(13-4)^2]
=16.5-[1.31-81]
=16.5-[31-81]
=16.5-(-50)
=80-(-50)
=130
\(a.\dfrac{7}{8}+\dfrac{1}{2}\text{=}\dfrac{11}{8}\)
\(b.\dfrac{5}{6}+\left(-2\right)\text{=}\dfrac{-7}{6}\)
\(c.\dfrac{2}{5}+\dfrac{-3}{8}\text{=}\dfrac{1}{40}\)
\(d.\dfrac{5}{7}-\dfrac{3}{8}\text{=}\dfrac{19}{56}\)
\(e.\dfrac{3}{4}-\dfrac{1}{2}+\dfrac{7}{6}\text{=}\dfrac{17}{12}\)
\(A=\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+\frac{1}{16}+\frac{1}{32}+\frac{1}{64}\)
\(\rightarrow A=\frac{3}{4}+\frac{1}{8}+\frac{1}{16}+\frac{1}{32}+\frac{1}{64}\)
\(\rightarrow A=\frac{7}{8}+\frac{1}{16}+\frac{1}{32}+\frac{1}{64}\)
\(\rightarrow A=\frac{15}{16}+\frac{1}{32}+\frac{1}{64}\)
\(\rightarrow A=\frac{31}{32}+\frac{1}{64}\)
\(\rightarrow A=\frac{63}{64}\)
\(A=\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+\frac{1}{16}+\frac{1}{32}+\frac{1}{64}\Rightarrow64A=32+16+8+4+2+1\Rightarrow64A=63\Rightarrow A=\frac{63}{64}\)
A = \(\frac{1}{3}-\frac{3}{4}-\frac{-3}{5}+\frac{1}{73}-\frac{1}{36}+\frac{1}{15}+\frac{-2}{9}\)
A = \(\left(\frac{1}{3}-\frac{2}{9}\right)-\left(\frac{3}{4}+\frac{1}{36}\right)+\left(\frac{3}{5}+\frac{1}{15}\right)+\frac{1}{73}\)
A = \(\left(\frac{3-2}{9}\right)-\left(\frac{27+1}{36}\right)+\left(\frac{9+1}{15}\right)+\frac{1}{73}\)
A = \(\frac{1}{9}-\frac{7}{9}+\frac{6}{9}+\frac{1}{73}\)
A = \(0+\frac{1}{73}=\frac{1}{73}\)
Làm
B = 1/3 - 3/4 - (-3)/5 + 1/73 - 1/36 + 1/15 + -2/9
B = 1/3 -3/4 + 3/5 +1/73 - 1/36 + 1/15 -2/9
B = [ 1/3 + 3/5 + 1/15 ] + [ -3/4 - 1/36 -2/9] + 1/73
B = [ 5/15 + 9/15 + 1/15 ] + [ -27/36 - 8/36 - 1/36 ] + 1/73
B = 1 + (-1) + 1/73
B = 1/73
HỌC TỐT Ạ
54 trang chiếm số phần trăm của quyển sách là :
1/4 = 25%
100% - 25% - 55% = 20 %
Quyển sách có số trang là :
54 : 20% = 54 : 20/100 = 54 x 100/20 = 270 trang
Đáp số : 270 trang
\(A=\frac{1}{2}-\frac{1}{2^4}+\frac{1}{2^7}-\frac{1}{2^{10}}+...+\frac{1}{2^{55}}-\frac{1}{2^{58}}\)
\(2^3.A=2^3-\frac{1}{2}+\frac{1}{2^4}-\frac{1}{2^7}+...+\frac{1}{2^{53}}-\frac{1}{2^{55}}\)
\(2^3.A+A=\left(2^3-\frac{1}{2}+\frac{1}{2^4}-\frac{1}{2^7}+...+\frac{1}{2^{53}}-\frac{1}{2^{55}}\right)+\left(\frac{1}{2}-\frac{1}{2^4}+\frac{1}{2^7}-\frac{1}{2^{10}}+...+\frac{1}{2^{55}}-\frac{1}{2^{58}}\right)\)
\(8A+A=2^3-\frac{1}{2^{58}}\)
\(9A=8-\frac{1}{2^{58}}\)
\(A=\frac{8-\frac{1}{2^{58}}}{9}\)
Ủng hộ mk nha ^-^
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