sánh đi nộp bài rồi làm hộ phép tính này lười làm a) 5/12 . (-3/4) + 7/12 . (-3/4) b) |2/5 – 1/2| – 7/2 – 1/10

Đáp án:

$a)$ $\dfrac{-3}{4}$
$b)$ $\dfrac{-7}{2}$

Giải thích các bước giải:
$a)$ $\dfrac{5}{12}$ $.$ $\dfrac{-3}{4}$ $+$ $\dfrac{7}{12}$ $.$ $\dfrac{-3}{4}$
$=$ $\dfrac{-3}{4}$ $.$ $($ $\dfrac{5}{12}$ $+$ $\dfrac{7}{12}$ $)$
$=$ $\dfrac{-3}{4}$ $.$ $1$
$=$ $\dfrac{-3}{4}$
$b)$ $|$ $\dfrac{2}{5}$ $-$ $\dfrac{1}{2}$ $|$ $-$ $\dfrac{7}{2}$ $-$ $\dfrac{1}{10}$
$=$ $\dfrac{1}{10}$ $-$ $\dfrac{7}{2}$ $-$ $\dfrac{1}{10}$
$=$ $($ $\dfrac{1}{10}$ $-$ $\dfrac{1}{10}$ $)$ $-$ $\dfrac{7}{2}$
$=$ $0$ $-$ $\dfrac{7}{2}$
$=$ $\dfrac{-7}{2}$
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