Cách làm cho bạn:
Ta có:
a) $12.(\frac{2}{3}−\frac{5}{6})^{2}$;
= $12.(\frac{4}{6}−\frac{5}{6})^{2}$
= $12.(\frac{−1}{6})^{2}$
= $12. \frac{1}{36}$
= $\frac{1}{3}$
b) $4.(\frac{−1}{2})^{3}−2.(\frac{−1}{2})^{2}+3.(\frac{−1}{2})+1$
$= 4.\frac{−1}{8}−2.\frac{1}{4}+\frac{−3}{2}+1$
$=\frac{−1}{2}−\frac{1}{2}+\frac{−3}{2}+\frac{2}{2}$
$=\frac{−3}{2}$
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