thực hiện phép tính (tính nhanh nếu có thể)
a) $\frac{-3}{7}$ + $\frac{15}{26}$ – ( $\frac{2}{13}$ – $\frac{3}{7}$ )
b) $\frac{1}{2}$ + $\frac{3}{4}$ -( $\frac{3}{4}$ – $\frac{4}{5}$ )
c) 2 . $\frac{3}{7}$ +( $\frac{2}{9}$ – 1$\frac{3}{7}$ ) – $\frac{5}{3}$ : $\frac{1}{9}$
Đáp án:
Giải thích các bước giải:
a)−37+1526−(213−37)a)−37+1526−(213−37)
=−37+1526−213+37=−37+1526−213+37
=1526−213=1526−213
=1526−426=1526−426
=1126=1126
b)12+34−(34−45)b)12+34−(34−45)
=12+34−34+45=12+34−34+45
=12+45=12+45
=510+810=510+810
=1310=1310
c)2.37+(29−137)−53:19c)2.37+(29−137)−53:19
=67+(29−107)−53.9=67+(29−107)−53.9
=67+29−107−453=67+29−107−453
=(67−107)+(29−453)=(67−107)+(29−453)
=−47−1339=−47−1339
=−3663−93163=−3663−93163
=−96763=−96763
Đáp án:
$a) \dfrac{-3}{7} +\dfrac{15}{26} -(\dfrac{2}{13} -\dfrac{3}{7})$
$=\dfrac{-3}{7} +\dfrac{15}{26} -\dfrac{2}{13} +\dfrac{3}{7}$
$=\dfrac{15}{26} -\dfrac{2}{13}$
$=\dfrac{15}{26} -\dfrac{4}{26}$
$=\dfrac{11}{26}$
$b) \dfrac{1}{2} +\dfrac{3}{4} -(\dfrac{3}{4} -\dfrac{4}{5})$
$=\dfrac{1}{2} +\dfrac{3}{4} – \dfrac{3}{4} +\dfrac{4}{5}$
$=\dfrac{1}{2} +\dfrac{4}{5}$
$=\dfrac{5}{10} +\dfrac{8}{10}$
$=\dfrac{13}{10}$
$c) 2 . \dfrac{3}{7} + (\dfrac{2}{9} -1\dfrac{3}{7}) -\dfrac{5}{3} : \dfrac{1}{9}$
$=\dfrac{6}{7} + (\dfrac{2}{9} -\dfrac{10}{7}) – \dfrac{5}{3} . 9$
$ =\dfrac{6}{7} + \dfrac{2}{9} -\dfrac{10}{7} – \dfrac{45}{3}$
$=(\dfrac{6}{7} -\dfrac{10}{7}) + (\dfrac{2}{9} -\dfrac{45}{3})$
$=\dfrac{-4}{7} – \dfrac{133}{9}$
$=\dfrac{-36}{63} – \dfrac{931}{63}$
$=\dfrac{-967}{63}$