`2/4 : 4/2` `5/14 xx 8/15` `9/17 + 4/9`

2 câu trả lời

$\text{$\dfrac{2}{4}$ : $\dfrac{4}{2}$ = $\dfrac{2}{4}$ × $\dfrac{2}{4}$ = $\dfrac{4}{16}$ = $\dfrac{1}{4}$ }$

$\text{$\dfrac{5}{14}$ × $\dfrac{8}{15}$ = $\dfrac{4}{21}$ }$

$\text{$\dfrac{9}{17}$ + $\dfrac{4}{9}$ = $\dfrac{81}{153}$ + $\dfrac{68}{153}$ = $\dfrac{149}{153}$}$

$\text{$\frac{2}{4}$: $\frac{4}{2}$= $\frac{2}{4}$x$\frac{2}{4}$= $\frac{2.2}{4.4}$= $\frac{4}{16}$= $\frac{1}{4}$ }$

$\text{$\frac{5}{14}$x $\frac{8}{15}$= $\frac{5x8}{14x15}$= $\frac{5x4x2}{7x2x5x3}$= $\frac{4}{7x3}$= $\frac{5}{21}$ }$

$\text{$\frac{9}{17}$+ $\frac{4}{9}$= $\frac{9x9}{17x9}$+ $\frac{4x17}{9x17}$ =$\frac{81}{153}$+ $\frac{68}{153}$= $\frac{81+68}{153}$= $\frac{149}{153}$ }$