a) 7/15+8/21x7/16 b)8/15-3/16x4/9 c)1/12:-1/4-(-1/8)mũ 2 giúp mik vs.

`a) 7/15 + 8/21 xx 7/16`

`= 7/15 + 56/336`

`= 7/15 + 1/6`

`= 14/30 + 5/30`

`= 19/30`

`b) 8/15 - 3/16 xx 4/9`

`= 8/15 - 12/144`

`= 8/15 - 1/12`

`= 32/60 - 5/60`

`= 27/60`

`= 9/20`

`c) 1/12 : (-1)/4 - (-1/8)^2`

`= 1/12. (-4) - 1/64`

`= (-1)/3 - 1/64`

`= (-64)/192 - 3/192`

`= (-67)/192`

Đáp án:

$a/$ $\dfrac{7}{15}$ $+$ $\dfrac{8}{21}$ $\times$ $\dfrac{7}{16}$

$=$ $\dfrac{7}{15}$ $+$ $\dfrac{1}{21}$ $\times$ $\dfrac{7}{2}$

$=$ $\dfrac{7}{15}$ $+$ $\dfrac{1}{3}$ $\times$ $\dfrac{1}{2}$

$=$ $\dfrac{7}{15}$ $+$ $\dfrac{1}{6}$

$=$ $\dfrac{19}{30}$

$b/$ $\dfrac{8}{15}$ $-$ $\dfrac{3}{16}$ $\times$ $\dfrac{4}{9}$

$=$ $\dfrac{8}{15}$ $-$ $\dfrac{1}{16}$ $\times$ $\dfrac{4}{3}$

$=$ $\dfrac{8}{15}$ $-$ $\dfrac{1}{4}$ $\times$ $\dfrac{1}{3}$

$=$ $\dfrac{8}{15}$ $-$ $\dfrac{1}{12}$

$=$ $\dfrac{9}{20}$

$c/$ $\dfrac{1}{12}$ $:$ $-$$\dfrac{1}{4}$ $-$ $($ $-$ $\dfrac{1}{8}$ $)$ $^{2}$

$=$ $-$ $\dfrac{1}{12}$ $:$ $\dfrac{1}{4}$ $-$ $($ $-$ $\dfrac{1}{8}$ $)$ $^{2}$

$=$ $-$ $\dfrac{1}{12}$ $\times$ $4$ $-$ $($ $-$ $\dfrac{1}{8}$ $)$ $^{2}$

$=$ $-$ $\dfrac{1}{12}$ $\times$ $4$ $-$ $\dfrac{1}{64}$

$=$ $-$ $\dfrac{1}{3}$ $-$ $\dfrac{1}{64}$

$=$ $-$ $\dfrac{67}{192}$

$#thuanhuy$

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