Rút gọn rồi tính: 6 , 8 2 - 3 , 2 2
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![](https://rs.olm.vn/images/avt/0.png?1311)
![](https://rs.olm.vn/images/avt/0.png?1311)
a) \(3-\frac{6}{8}-\frac{2}{4}\)
\(=\frac{18}{8}-\frac{6}{8}-\frac{4}{8}\)
\(=\frac{18-6-4}{8}\)
\(=\frac{8}{8}=1\)
b) \(\frac{5}{6}-\frac{1}{2}+2\)
\(=\frac{5}{6}-\frac{3}{6}+\frac{12}{6}\)
\(=\frac{5-3+12}{6}\)
\(=\frac{14}{6}=\frac{7}{3}\)
\(a.3+\frac{6}{8}-\frac{2}{4}\\ =\frac{3}{1}+\frac{6}{8}-\frac{2}{4}\\ =\frac{24}{8}+\frac{6}{8}-\frac{4}{8}\\ =\frac{24+6-4}{8}\\ =\frac{26}{8}\\ =\frac{13}{4}\)
\(b.\frac{5}{6}-\frac{1}{2}+2\\ =\frac{5}{6}-\frac{1}{2}+\frac{2}{1}\\ =\frac{5}{6}-\frac{3}{6}+\frac{12}{6}\\ =\frac{5-3+12}{6}\\ =\frac{14}{6}\\ =\frac{7}{3}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(C=\left(\frac{x}{2}-y\right)^3-3.2.\left(\frac{x}{2}-y\right)^2+3.2^2\left(\frac{x}{2}-y\right)-2^3=\left(\frac{x}{2}-y-2\right)^3\)
với \(x=206,y=1\Rightarrow C=\left(\frac{x}{2}-y-2\right)^3=\left(\frac{206}{2}-1-2\right)^3=1000\text{ }000\)
![](https://rs.olm.vn/images/avt/0.png?1311)
Bài 2:
a: 2/6x5/3=10/18=5/9
b: 11/9x5/10=55/90=11/18
c: 3/9x6/8=1/3x3/4=1/4
d: 4/9x12/16=48/144=1/3
e: 25/15x6/7=5/3x6/7=30/21=10/7
f: 6/10x15/20=90/200=9/20
Bài 1
4/5 x 6/7= 24/35
2/9 x 1/2= 2/18= 1/9
1/2 x 8/3= 8/6= 4/3
7/9 x 6/5= 42/45= 14/15
8/7 x 5/9= 40/63
10/11 x 22/15= 220/165= 4/3
Bài 2
2/6 x 5/3= 1/3 x 5/3=5/9
11/9 x 5/10= 11/9 x 1/2= 11/18
3/9 x 6/8= 1/3 x 3/4 =3/12= 1/4
4/9 x 12/16= 4/9 x 3/4= 12/36= 1/3
25/15 x 6/7= 5/3 x 6/7= 30/21= 10/7
6/10 x 15/20= 3/5 x 3/4= 9/20
![](https://rs.olm.vn/images/avt/0.png?1311)
1, Rút gọn rồi tính
a) \(\frac{4}{5}+\frac{3}{15}\)
= \(\frac{4}{5}+\frac{1}{5}\)
= \(\frac{5}{5}\)
= \(1\)
b) \(\frac{2}{3}+\frac{32}{24}\)
= \(\frac{2}{3}+\frac{4}{3}\)
= \(\frac{6}{3}\)
= \(2\)
c) \(\frac{5}{6}+\frac{15}{18}\)
= \(\frac{5}{6}+\frac{5}{6}\)
= \(\frac{10}{6}\)
= \(\frac{5}{3}\)
2, Tính rồi rút gọn
a) \(\frac{8}{15}+\frac{2}{3}\)
= \(\frac{8}{15}+\frac{10}{15}\)
= \(\frac{18}{15}\)
= \(\frac{6}{5}\)
b) \(\frac{3}{7}+\frac{4}{8}\)
= \(\frac{24}{56}+\frac{28}{56}\)
= \(\frac{52}{56}\)
= \(\frac{13}{14}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
\(2\sqrt{\left(-5\right)^6}+3\sqrt{\left(-2\right)^8}.\)
\(=2\sqrt{\left(\left(-5\right)^3\right)^2}+3\sqrt{\left(\left(-2\right)^4\right)^2}\)
\(=2\cdot\left(-5\right)^3+3\cdot\left(-2\right)^4\)
\(=2\cdot125+3\cdot16=250+48=298\)
\(\Rightarrow2\sqrt{\left(-5\right)^6}+3\sqrt{\left(-2\right)^8}=298\)
\(2\sqrt{\left(-5\right)^6}+3\sqrt{\left(-2\right)^8}\)
\(=2\times125+3\times16\)
\(=250+48\)
\(=298\)
![](https://rs.olm.vn/images/avt/0.png?1311)
a) \(\dfrac{5}{6}-\dfrac{2}{14}\)
\(=\dfrac{5}{6}-\dfrac{1}{7}\)
\(=\dfrac{35}{42}-\dfrac{6}{42}\)
\(=\dfrac{29}{42}\)
b) \(\dfrac{5}{20}-\dfrac{1}{6}\)
\(=\dfrac{1}{4}-\dfrac{1}{6}\)
\(=\dfrac{3}{12}-\dfrac{2}{12}\)
\(=\dfrac{1}{12}\)
c) \(\dfrac{5}{9}-\dfrac{3}{12}\)
\(=\dfrac{5}{9}-\dfrac{1}{4}\)
\(=\dfrac{20}{36}-\dfrac{9}{36}\)
\(=\dfrac{11}{36}\)
d) \(8-\dfrac{4}{6}\)
\(=\dfrac{48}{6}-\dfrac{4}{6}\)
\(=\dfrac{44}{6}=\dfrac{22}{3}\).
![](https://rs.olm.vn/images/avt/0.png?1311)
8/15 + 2/3 = 18/15
Rút gọn kết quả thành 6/5
3/7 + 4/8 = 52/56
Rút gọn kết quả thành 13/14
8/15+2/3=8/15+10/15=18/15=6/5
3/7+4/8=24/56+28/56=52/56=13/14
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\frac{2}{8}\)+\(\frac{5}{6}\)
=\(\frac{1}{4}\)+\(\frac{5}{6}\)
=\(\frac{6}{24}\)+\(\frac{20}{24}\)
=\(\frac{13}{12}\)
![](https://rs.olm.vn/images/avt/0.png?1311)
Lời giải:
$\frac{1}{2}+\frac{1}{2}=\frac{1+1}{2}=\frac{2}{2}=1$
$\frac{3}{8}+\frac{1}{8}=\frac{3+1}{8}=\frac{4}{8}=\frac{1}{2}$
$\frac{7}{9}+\frac{5}{9}=\frac{7+5}{9}=\frac{12}{9}=\frac{3\times 4}{3\times 3}=\frac{4}{3}$
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\dfrac{6}{9}\)\(\times\dfrac{2}{8}\)=\(\dfrac{2}{3}\times\dfrac{1}{4}\)
\(=\)\(\dfrac{1}{6}\)
tick mình nhé