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Thay dấu ba chấm bởi x rồi tìm x.
Chẳng hạn:
\(a) \) \(\dfrac{7}{9}-\dfrac{x}{3}=\dfrac{1}{9}\)
\(\Rightarrow\dfrac{x}{3}=\dfrac{7}{9}-\dfrac{1}{9}\)
\(\Rightarrow\dfrac{x}{3}=\dfrac{6}{9}=\dfrac{2}{3}\)
Vậy x = 2
Đáp số:
a) x = 2
b) x = 3
c) x = 7
d) x =19.
![](https://rs.olm.vn/images/avt/0.png?1311)
Trả lời
(2+3)4.42= 54.42= 625.16=10000
52.22.4= 25.4.4=400
Học tốt. k mik nha
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1) 1998.1998 - 2000.1996
= 1998.1998 - 1998.1996 - 2.1996
= 2.1998 - 2.1996
= 2.2
= 4
2)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(2,5-\frac{2}{3}.\frac{3}{4}+3\frac{1}{6}\)
\(=\frac{5}{2}-\frac{2}{3}.\frac{3}{4}+\frac{19}{6}\)
\(=\frac{3}{4}.\frac{10}{3}-\frac{2}{3}.\frac{3}{4}-\frac{3}{4}.\frac{38}{9}\)
\(=\frac{3}{4}.\left(\frac{10}{3}-\frac{2}{3}-\frac{38}{9}\right)\)
\(=\frac{3}{4}.\left(\frac{30}{9}-\frac{6}{9}-\frac{38}{9}\right)\)
\(=\frac{3}{4}.\frac{-14}{9}\)
\(=-\frac{7}{6}\)
\(2,5-\frac{2}{3}\times\frac{3}{4}+3\frac{1}{6}\)
\(=\frac{5}{2}-\frac{1}{2}+3+\frac{1}{6}\)
\(=2+3+\frac{1}{6}\)
\(=5\frac{1}{6}\)
Chúc bn học tốt !!!
![](https://rs.olm.vn/images/avt/0.png?1311)
\(a,81^3\cdot\frac{1}{9^2}:3^3=\left(9^2\right)^3\cdot\frac{1}{9^2}:3^3=9^6\cdot\frac{1}{9^2}\cdot\frac{1}{3^3}=\frac{9^6}{9^2}\cdot\frac{1}{3^3}=9^4\cdot\frac{1}{3^3}=\left(3^2\right)^4\cdot\frac{1}{3^3}=\frac{3^8}{3^3}=3^5\)
\(b,625^4:25^2=\left(5^4\right)^4:\left(5^2\right)^2=5^{16}:5^4=5^{12}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
Ta có:
13 + 23 + ... + n3 = [1+2+3+...+n]2
Áp dụng vào bài toán:
13 + 23 + 33 + 43 + 53 = [1+2+3+4+5]2 = 152