/ là gì bạn

a)

= \(\dfrac{128.9^3}{65.8^2}\)

= \(\dfrac{128.729}{7776.64}\)

=\(\dfrac{93312}{497664}\)

= \(\dfrac{1}{3}\)

a) \(\dfrac{\left(0,6\right)^5}{\left(0,2\right)^6}=\dfrac{\left(0,2.3\right)^5}{\left(0,2\right)^5.\left(0,2\right)}=\dfrac{\left(0,2\right)^5.3^5}{\left(0,2\right)^5.\left(0,2\right)}=\dfrac{3^5}{0,2}=\dfrac{243}{0,2}=1215\)

c) \(2:\left(\dfrac{1}{2}-\dfrac{2}{3}\right)^2=2:\left(\dfrac{3}{6}-\dfrac{4}{6}\right)^2=2:\left(-\dfrac{1}{6}\right)^2=2:\dfrac{1}{36}=72\)

3/3x6 + 3/6x9 + 3/9x12 + 3/12x15 + 3/15x18

= 1/3 - 1/6 + 1/6 - 1/9 + ... + 1/15 - 1/18

= 1/3 - 1/18

= 5/18

\(\frac{3}{3\times6}+\frac{3}{6\times9}+\frac{3}{9\times12}+\frac{3}{12\times15}+\frac{3}{15\times18}\)

=\(3\times\left(\frac{1}{3\times6}+\frac{1}{6\times9}+\frac{1}{9\times12}+\frac{1}{12\times15}+\frac{1}{15\times18}\right)\)

=\(3\times\left(\frac{1}{3}\times\frac{1}{6}+\frac{1}{6}\times\frac{1}{9}+\frac{1}{9}\times\frac{1}{12}+\frac{1}{12}\times\frac{1}{15}+\frac{1}{15}\times\frac{1}{18}\right)\)

=\(3\times\left(\frac{1}{3}\times\frac{1}{18}\right)\)

=\(3\times\frac{1}{54}=\frac{3}{54}=\frac{1}{18}\)

21

\(b,\frac{10^3+5x10^2+5^3}{6^3+3x6^2+3^3}\)

\(=\frac{5\left(200+10^2+5^2\right)}{3\left(72+6^2+3^2\right)}\)

\(=\frac{5\left(200+100+25\right)}{3\left(72+36+9\right)}\)

\(=\frac{5.325}{3.117}\)

\(=\frac{125}{27}\)

\(6,9+8,4+3,1+1,6+5,5+9,8+4,5+0,2\\ =\left(6,9+3,1\right)+\left(8,4+1,6\right)+\left(5,5+4,5\right)+9,8\\ =10+10+10+9,8\\ =39,8\)

\(\frac{2}{1.3}+\frac{3}{3.6}+\frac{4}{6.10}+\frac{5}{10.15}+\frac{6}{15.21}\)

= \(1-\frac{1}{3}+\frac{1}{3}-\frac{1}{6}+\frac{1}{6}-\frac{1}{10}+\frac{1}{10}-\frac{1}{15}+\frac{1}{15}-\frac{1}{21}\)

= \(1-\frac{1}{21}\)

= \(\frac{20}{21}\)

Ủng hộ mk nha !!! ^_^