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giúp mình bài này với
bạn nam đọc 1 quyển sách trong 3 ngày . ngày 1 đọc 1 phần 3 số trang . ngày thứ 2 đọc 2 phần 5 số trang còn lại .ngày 3 đọc 36 trang còn lại. hỏi quyển sách có bao nhiêu trang
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6A=5.7.6+7.9.6+9.11.6+11.13.6+13.15.6+...+99.101.6
6A=5.7.(9-3)+7.9.(11-5)+9.11.(13-7)+11.13.(15-9)+13.15.(17-11)+...+99.101.(103-97)
6A=-3.5.7+5.7.9-5.7.9+7.9.11-7.9.11+9.11.13-9.11.13+11.13.15-11.13.15+13.15.17-...-97.99.101+99.101.103
6A=99.101.103-3.5.7 => A=(99.101.103-3.5.7)/6
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A, 7x - x = 5^21 : 5^19 + 3 . 2^2 - 7^0
6x = 5^2 + 3 . 4 - 1
6x = 25 + 12 - 1
6x = 37 - 1
6x = 36
x = 6.
B, mình giải ra nhưng số to quá. Bạn thử kiểm tra lại đề xem.
C, 7x - 2x = 6^17 : 6^15 + 44 : 11
5x = 6^2 + 4
5x = 40
x = 8.
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\(a,\dfrac{7}{-25}+\dfrac{-18}{25}+\dfrac{4}{23}+\dfrac{5}{7}+\dfrac{19}{23}\)
\(=\left(\dfrac{-7}{25}+\dfrac{-18}{25}\right)+\left(\dfrac{4}{23}+\dfrac{19}{23}\right)+\dfrac{5}{7}\)
\(=\left(-1\right)+1+\dfrac{5}{7}\)
\(=0+\dfrac{5}{7}=\dfrac{5}{7}\)
b, \(\dfrac{7}{19}.\dfrac{8}{11}+\dfrac{7}{19}.\dfrac{3}{11}+\dfrac{12}{19}\)
\(=\dfrac{7}{19}\left(\dfrac{8}{11}+\dfrac{3}{11}\right)+\dfrac{12}{19}\)
\(=\dfrac{7}{19}.1+\dfrac{12}{19}\)
\(=\dfrac{7}{19}+\dfrac{12}{19}=1\)
a. \(\dfrac{7}{-25}+\dfrac{-18}{25}+\dfrac{4}{23}+\dfrac{5}{7}+\dfrac{19}{23}\)
\(=\left(\dfrac{-7}{25}+\dfrac{-18}{25}\right)+\left(\dfrac{4}{23}+\dfrac{19}{23}\right)+\dfrac{5}{7}\)
\(=-1+1+\dfrac{5}{7}\)
\(=\dfrac{5}{7}\)
b. \(\dfrac{7}{19}\cdot\dfrac{8}{11}+\dfrac{7}{19}\cdot\dfrac{3}{11}+\dfrac{12}{19}\)
\(=\dfrac{7}{19}\left(\dfrac{8}{11}+\dfrac{3}{11}\right)+\dfrac{12}{19}\)
\(=\dfrac{7}{19}\cdot1+\dfrac{12}{19}\)
\(=\dfrac{7}{19}+\dfrac{12}{19}\)
\(=1\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\dfrac{7}{-25}+\dfrac{18}{25}+\dfrac{4}{23}+\dfrac{5}{7}+\dfrac{19}{23}\)
=\(\left(\dfrac{-7}{25}+\dfrac{18}{25}\right)+\left(\dfrac{4}{23}+\dfrac{19}{23}\right)+\dfrac{5}{7}\)
= \(\dfrac{11}{25} +1+\dfrac{5}{7}\)
= \(1\dfrac{11}{25}+\dfrac{5}{7}\)
= \(2\dfrac{27}{175}\)
b) \(-2+\dfrac{15}{19}+\dfrac{-15}{17}+\dfrac{15}{23}+\dfrac{4}{19}\)
=\(-2+\left(\dfrac{ }{ }\right)\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(A=\frac{7}{19}.\frac{8}{11}.\frac{7}{19}:\frac{3}{11}+\frac{12}{19}\)
\(A=\left(\frac{7}{19}\right)^2.\frac{8}{11}.\frac{11}{3}+\frac{12}{19}\)
\(\Rightarrow A=\left(\frac{7}{19}\right)^2.\frac{8}{3}+\frac{12}{19}\)
\(\Rightarrow A=\frac{392}{1083}+\frac{12}{19}\)
\(\Rightarrow A=\frac{1076}{1083}\)